Red Light and Testicle Function

Most organs and glands of the body are covered by several inches of either bone, muscle, fat, skin or other tissues, making direct light exposure impractical, if not impossible. However, one of the notable exceptions is the male testes.

Is it advisable to shine red light directly on one’s testicles?


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Research is highlighting several interesting benefits to testicular red light exposure:

Fertility Boosted?

Sperm quality is the primary measure of fertility in men, as the viability of spermatozoa is generally the limiting factor to successful reproduction (from the male’s side).

Healthy spermatogenesis, or the creation of sperm cells, happens in the testicles, not so far from the production of androgens in the Leydig cells. The two are highly correlated in fact – meaning that high testosterone levels = high sperm quality and vice versa. It’s rare to find a low testosterone man with great sperm quality.

Sperm are produced in the seminiferous tubules of the testes, in a multi-step process involving several cell divisions and maturation of these cells. Various studies have established a very linear relationship between ATP/energy production and spermatogenesis:

  • Drugs and compounds which interfere with mitochondrial energy metabolism in general (i.e. Viagra, ssris, statins, alcohol, etc.) have an extremely negative effect on sperm production.
  • Drugs/compounds which support ATP production in mitochondria (thyroid hormones, caffeine, magnesium, etc.) boost sperm counts and general fertility.

More so than other bodily processes, sperm production is highly dependent on ATP production. Given that red & infrared light both enhance ATP production in mitochondria, according to the leading research in the field, it should come as no surprise that red/infrared wavelengths have been shown to boost testicular sperm production and viability of the sperm in various animal studies. Conversely, blue light, which harms the mitochondria (suppressing ATP production) reduces sperm count/fertility.

mitochondria and red light in sperm
Sperm may have more energy to ‘swim’ after stimulation by red light

This applies not only to the sperm production in the testicles, but also directly to the health of free sperm cells post-ejaculation. For example studies have been done on in vitro fertilization (IVF), showing superior outcomes under red light in both mammals and fish sperm. The effect is especially profound when it comes to sperm motility, or ability to ‘swim’, as the tail of sperm cells are powered by a row of red light sensitive mitochondria.


  1. In theory, red light therapy properly applied to the testicle area shortly before sexual intercourse could produce a greater chance of successful fertilization.
  2. Furthermore, consistent red light therapy over the days prior to sexual intercourse might further increase chances, not to mention reduce chances of abnormal sperm production.

Testosterone Levels Potentially Tripled?

It has been known scientifically since the 1930s that light in general can help males to produce more of the androgen testosterone. Initial studies back then examined how isolated light sources on the skin and body affect hormone levels, showing a significant improvement by using incandescent bulbs and artificial sunlight.

Some light, it seems, is good for our hormones. Conversion of skin cholesterol into vitamin D3 sulfate is a direct link. Though perhaps more importantly, the improvement in oxidative metabolism and ATP production from red/infrared wavelengths has broad reaching, and often underestimated, effects on the body. After all, cellular energy production is the basis of all functions of life.

More recently, studies have been done on direct sunlight exposure, firstly to the torso, which reliably increases male’s testosterone levels by anywhere from 25% to 160% depending on the person. Sunlight exposure directly to the testes though has an even more profound effect, boosting testosterone production in Leydig cells by an average of 200% – a large increase over baseline levels.

Studies linking light, particularly red light, to the testicular function of animals have been performed for almost 100 years now. Initial experiments focused on male birds and small mammals such as mice, showing effects such as sexual activation and recrudescence. Testicular stimulation by red light has been researched for almost a century, with studies linking it to healthy testicular growth and superior reproductive outcomes in almost all cases. More recent human studies support the same theory, showing potentially even more positive results compared to birds/mice.

Does red light on testes really have dramatic effects on testosterone?

testosterone molecule
Testosterone molecule as produced by humans

Testicular function, as mentioned above, is dependent on energy production. While this can be said about practically any tissue in the body, there is evidence that it is especially true for the testes.

Explained in greater detail on our red light therapy page, the mechanism via which red wavelengths work is supposedly to stimulate ATP production (which can be thought of as cellular energy currency) in our mitochondria’s respiratory chain (look into cytochrome oxidase – a photoreceptive enzyme – for more info), increasing the energy available to the cell – this applies to Leydig cells (testosterone producing cells) just as much. Energy production and cellular function are commensurate, meaning more energy = more testosterone production.

More so than that, whole body energy production, as correlated with / measured by active thyroid hormone levels, is known to stimulate steroidogenesis (or testosterone production) directly in the Leydig cells.

Another potential mechanism involves a seperate class of photoreceptive proteins, known as ‘opsin proteins’. The human testes are especially abundant with various of these highly specific photoreceptors including OPN3, which are ‘activated’, much like cytochrome, specifically by wavelengths of light. Stimulation of these testicular proteins by red light induces cellular responses that may ultimately lead to increased testosterone production, amongst other things, although research is still in the preliminary stages regarding these proteins and metabolic pathways. These type of photoreceptive proteins are also found in the eyes and also, interestingly, the brain.


  1. Some researchers speculate that red light therapy directly on the testicles for short, regular periods would raise testosterone levels over time.
  2. Downstream this might potentially lead to a holistic effect on the body, raising focus, improving mood, increasing muscle mass, bone strength and lowering excess body fat.


Type of light exposure is crucial

Red light can come from a variety of sources; it is contained in the wider spectra of sunlight, most home/work lights, street lights and so on. The problem with these light sources is that they also contain contradictory wavelengths such as UV (in the case of sunlight) and blue (in the case of most home/street lights). Additionally, the testicles are especially sensitive to heat, more so than other parts of the body. There’s no point applying beneficial light if you are simultaneously cancelling the effects with harmful light or excess heat.

Blue & UV light’s effects

Metabolically, blue light can be thought of as the opposite of red light. While red light potentially improves cellular energy production, blue light worsens it. Blue light specifically damages cell DNA and the cytochrome enzyme in mitochondria, preventing ATP and carbon dioxide production. This can be positive in certain situations such as acne (where the problematic bacteria are killed), but over time in humans this leads to an inefficient metabolic state similar to diabetes.

Red Light vs. Sunlight on testicles

Sunlight has definite beneficial effects – vitamin D production, improved mood, increased energy metabolism (in small doses) and so on, but it is not without its downsides. Too much exposure and you not only lose all benefits, but create inflammation and damage in the form of sunburn, eventually contributing the skin cancer. Sensitive areas of the body with thin skin are especially prone to this damage and inflammation from sunlight – no area of the body more so than the testes. Isolated sources of red light such as LEDs are well studied, seemingly with none of the harmful blue & UV wavelengths and so no risk of sunburn, cancer or testicular inflammation.

Don’t heat the testicles

Male testicles hang outside of the torso for a specific reason – they operate most efficiently at 35°C (95°F), which is a full two degrees below normal body temperature of 37°C (98.6°F). Many types of lamps and bulbs used by some for light therapy (such as incandescents, heat lamps, infrared lamps at 1000nm+) give off a significant amount of heat and therefore are NOT suitable for use on the testicles. Heating the testicles while attempting to apply light would give negative results. The only ‘cold’/efficient sources of red light are LEDs.

Bottom Line

  • Red or infrared light from an LED source (600-950nm) has been studied for use on the male gonads
    • Some of the potential benefits are detailed above
  • Sunlight can also be used on the testes but only for short periods and it is not without risks.
  • Avoid exposure to blue/UV.
  • Avoid any sort of heat lamp/incandescent bulb.

The most studied form of red light therapy is from LEDs and lasers. Visible red (600-700nm) LEDs seem to be optimal.

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111 thoughts on “Red Light and Testicle Function

  1. Alex Fergus says:

    Great article! I’ll be sharing on my social media pages!

    So I have a question for you, you don’t mention anything about the ideal time exposure to reap the benefits?
    Are we talking a few minutes a day, or hours? Or is more simply better?

    Also, what about light intensity? I have a pretty weak red LED bulb here, it doesn’t put out much light but its red light. Would that be enough to gain the T boosting benefits?

    Looking forward to hearing more.


    • John says:

      Hi Alex, good questions.
      There is more information on our red light therapy page ( regarding ideal application times etc.

      Basically…light intensity is important, as lower intensity lights (<100mW/cm2 for LEDs) won't penetrate much past the surface layer of skin. Some LED devices, such as panel or UFO lights, are too spread out or emit the light on such as wide angle (90+ degrees) that they won't penetrate either.
      Other red light technologies such as infrared bulbs, heat lamps or incandescents may require 250w+ for the same intensity due to lower energy efficiency, and you would have to hold them so close that they would burn you - however they are much less suitable as the large heat output will heat up the testes beyond their 35 degrees Celsius (95 degrees Fahrenheit) optimal temperature range well before providing any benefits.

      Assuming you have an ideal source of red light, a session anywhere from 2-5 minutes exposure at a time would be good. Ideally one should separate sessions by several hours to get maximum benefits, however you can do it every day, or at least 3 times a week to see some results. With light therapy in general (and especially on the testicles), it is NOT a case of 'the more the better' for several reasons involving the mitochondrial respiratory chain. In addition, more than 30 minutes exposure, even with a highly efficient LED/laser light, would heat up the testicles too much, which lowers function. There is a balance to achieve somewhere around 2-5 minutes continuous exposure time, depending on your light source - after that give the balls a break to cool off!
      Hope that helps!

      • Alexander says:


        I’ve recently started using a red light on my testicles and the effects on my testosterone have been pretty profound.

        However, I have noticed that I have been waking up in the middle of the night more than usual and being unable to get back to sleep.

        I’m sure it’s the red light, but do you have any clue as to the exact mechanism? I’m unsure whether it relates to use on the testicles or perhaps occasional use on my face (I find it helps with eye strain from my job).

        Fantastic blog by the way.

  2. Pmold says:


    Infrared is harmful to the testis. Please read this below research paper. It says that 670 nm is good for testis but not infrared above > 830nm. But in your web site you have suggested to use infrared LED on testicals ???? this may damage it … Let me know you opinion.

    • John says:

      Hi there, that’s not exactly what they are saying in the research paper discussion, though I can see why you might interpret it that way.
      They’re saying extremely high doses of infrared laser light may be harmful, but reasonable doses beneficial.

      The laser power they use in this study is a factor of 10-30 times higher than the upper limit for most studies, and a factor of 100-300 times higher than most reported beneficial doses. In fact the laser they are using is typically used for laser hair removal and ablation (burning) surgery. You could instantly light a match or pop a balloon with it.

      Due to the penetrative native of infrared, and its likelihood of being absorbed by water….well they are basically cooking/burning the rat’s testicles by using 360J/cm2/day (200 mW × 30 min). 670nm (or visible red) is safer and still beneficial at this same high dose because it doesn’t have such a definite warming effect on cellular water and doesn’t penetrate as well. As I’ve mentioned above, the testes are especially sensitive to heat.

      Infrared LEDs strength won’t get anywhere near to these high ‘testicle sizzling’/’match lighting’ doses achieved by the industrial lasers in that study. Literally every study using a normal infrared dose (0.5 to 30 J/cm2/day) on the testes shows positive outcomes, so I wouldn’t jump to conclude that infrared is bad for the testes just yet..
      I hope that puts things into perspective and assuages any infrared LED phobia!

      • Pmold says:

        Thanks for the clarification. Did you find any research papers that says infrared LEDs are beneficial for testicals ? . Can you share it, if you have any ??????

        • John says:

          Sure. I’ve got them referenced above but here are links.
          This study shows exactly what we are talking about (lower dose beneficial for testes, higher dose not). They’re actually searching for the threshold.

          There are more explaining the biphasic dose response – &

          Infrared on human testes –
          Infrared on human sperm –

          It’s all in the dose…Hope that helps!

          • Josh says:

            Hi John,
            You said that ” Literally every study using a normal infrared dose (0.5 to 30 J/cm2/day) on the testes shows positive outcomes”, but also (further above) that “light intensity is important, as lower intensity lights (<100mW/cm2 for LEDs) won't penetrate much past the surface layer of skin".

            So I'm confused, as there seems to be a bit of a contradiction there (0.5 J could come from a very low-power LED or laster, I assume…).
            I understand that maybe the research is still being conducted and we don't know the final answer for the effective and safety thresholds.

            Here's the thing: my wife has a 10 mW/cm2 (at 3-inches distance) LED machine with visible red + infrared diodes (~650 and ~850 nm wavelengths), for surface skin therapy (supposedly to help with facial acne and such). Would I derive any benefit from shining this device at my balls?
            Say, at 15 minutes per day, that would be 9 J total dose if my calculations are right, which is within the 0.5 to 30 J range you mentioned as beneficial. A full 30 minutes of exposure to that device would mean 18 J, close to the midpoint of the aforementioned range. Yet, are those 18 J penetrating deeper under the scrotal sack skin or not…?

            Thanks for your insight!

      • S. says:

        Hi. I have one testicle due to T cancer. So I inject T. But I experience noticeable peeks and valleys in T. If I do not inject my T plummets. I have a Hairmax LaserBand 82 device for hair loss. I also have Graves Disease. The company tells me it emits 655 nm. It does not generate heat on my scalp. Could applying this to my testicle work to elevate and even out T, and assist in testicle atrophy due to T injections? What application time and frequency would you recommend? Please advise. Thanks S.

        • Joe says:

          I do not know the power density (a.k.a. light intensity – in mW/cm2) of that, so cannot answer any of your questions. It might be useful, or might not, depending on the light intensity and others factors like EMFs.

    • John says:

      Lasers are good, but there’s no reason to believe they’re any better than LEDs for the purpose of light therapy. A photon is a photon, regardless of source – your cells don’t know the difference. The ‘coherent’ state of laser light is gone as soon as the light passes 0.1mm of skin.
      Low level lasers will eventually be phased out in my opinion. I think they’ve only lasted this long because of the marketing appeal – ‘laser’ sounds clinical and interesting. Companies invest in research with them because they’re too expensive for patients to buy for using at home.
      You can get nearly all of the same benefits from using LED light, and you can calculate dose and control strength just the same.

    • JR says:

      Old post, but maybe you’ll still see it.
      I have a red light device, took T test came in a 390 , I toast my boys 5 days a week , at 5 min each session, for 2 months. Went back in for another test, and I was at 485 – the highest in my lifetime naturally. The first test was at 0830 am after a great nights sleep, no booze. The second test I had a sunus infection and the blood was drawn at 10am – and I was awake since 0430. I was expecting to see low T and I was shocked by the results.

  3. neos says:

    Hi, my interest is in raising test levels without raising sperm count as my wife and i are not ready to have a baby yet.
    My question is about heating up the testies. Does heat kill more than just the sperm? Does heat negatively effect test production?
    Im wondering if its possible to raise my test level and kill my sperm at the same time with red light and some heat. I have a 30 watt red LED that does get rather hot if you press it against your skin for longer than a minute. Ive been using it on my balls for a couple weeks and have noticed an improvement in my mood and sense of well being similiar to when i was on trt a couple years ago. I press it right into my sack and it penatrates all the way through and makes my boys glow red while making them toasty at the same time.
    I know a hot tub and tight undies will negatively effect sperm production, so can i safely heat up my boys with this red light, kill sperm and jack up my test at the same time?
    Its a kessil h150 red that im using on my nuts
    Thanks in advance

    • Joe says:

      Hi Neos, unfortunately I think your goals of raising test without raising sperm count/quality are diametrically opposed. The Leydig cells (testosterone producing) are directly regulated by the Sertoli cells (sperm producing). So to have high testosterone levels, you need high sperm function first. Heating the testes therefore does negatively affect test production.
      I do not recommend applying any heat to the testes whatsoever.
      I suppose you could achieve your goal by using exogenous hormone supplementation, but I also do not recommend that unless under constant supervision of qualified medical doctors.

  4. Luke says:

    Really interesting – I have a damaged testicle from many years ago – perhaps this light would help!

    • Joe says:

      Hi John,
      I don’t know. Seems pretty weak. I found their output is around 65mW/cm2 right on the panel. Probably drops to nothing after a few inches. I wouldn’t recommend something so underpowered, especially for pain (where you need the higher power densities to get more penetration). You could give it a try anyway. It’s probably going to be more effective pressed on the testes than it ever would be for pain, ironically, but you can get much more powerful products for less money.

  5. Jeff Allan says:

    hi what product do you recommend for vasodilation and ED relief and how is the proceedure administered ie do you physically hold the light on your testes or a few centimetres away.

    • Joe says:

      Near infrared lights penetrate deeper than red so are perhaps more useful for ED. For ED one would presumably just use the light near and around the penis area, not necessarily on the testes for that, it would be better below the testes in the area between the scrotum and anus, or above the penis in the pubic hair area.

  6. Mod says:

    Hi Joe,

    What is the optimal distance for shining red light(mini 670nm LED red light device) on testicles? I remember using it very close to my testicles, 4 cm, for 5-7 minutes. Then, later on I used it for 10 minutes at a 16 cm distance. Do you think the close distance affected me negatively?

    • Joe says:

      Hi Mo,
      I don’t know. I wish there was more hard data to go on.
      I don’t think the close distance will give negative results, you just need to make sure there is no significant heat build up, hence perhaps only using it for a minute or two.

  7. Mod says:

    Hi Joe,

    Well, from now on I’ll use it for 3 minutes at 4 cm. Also, I’ve been using it on my thyroid lately to experiment. Do you think shining red light for 10 minutes so close to neck skin(touching thyroid) poses a problem and/or possibly a contraindication? Thanks a lot!

  8. Mod says:

    Hi Joe,

    The amount of heat generated by the lamp after ten minutes is actually very bearable. It is almost a cool red heat. I was wondering if I could use it for a maximum of 20 minutes on testicles. Given that I use at 10 cm because any distance less than that is quite uncomfortable.

    • Joe says:

      Yeah, sure, I don’t think you will notice anything negative from doing that in that case. As long as you aren’t heating up the testes, it’s just like light therapy anywhere else on the body.

  9. Mod says:

    It is obvious that heat is detrimental to the testes. Do you think heat should be avoided at all cost when shining light on the testes even the really bearable warmthy heat?

  10. Mod says:

    Hey Joe,

    I have been using red light on my testes for about two weeks now. I used them at a distance anywhere from ~10cm – 4cm; adjusting time length accordingly. At first I used it once a day for 5 minutes at a further distance then I began to use it twice a day for shorter sessions at shorter distances. Do you think I over did it? Also, do the testicles need to rest after continuous exposure(daily and two sessions a day) or is continuous exposure is all fine? Do you think I hurt myself?

  11. Matt says:

    Hi I have a question,

    I borrowed a friend’s class 4 laser and set it to 10 watts (goes up to 60) and used it on my penis because I have a painful spot. It was near the testicles. Could I have done damage to the testicles?? It’s made for injuries but I didn’t know you weren’t supposed to use it near the testicles. Thanks!

  12. Mod says:

    Hi Joe,

    I have been recently using red light along side my laptop. I figured red light would balance the negative blue light emitted from the laptop. Do you think it is a problem to be exposed to red light for 3 continuous hours? Also, I noticed something strange, I feel l like I’m potent after the exposure.

    • Joe says:

      I don’t think it’s a problem at all. I do the same frequently.
      Although I haven’t seen any studies on potency from long red light exposure, many people online seem to notice and discuss that. It’s likely a strong full body change in nitric oxide and carbon dioxide levels, both helping with potency.

  13. Mod says:

    Yeah. I wholeheartedly agree. I have been using the red light 670 device for over 6 weeks now. I have noticed very astounding results. Now, I’ll try the other device NIR. Do you think I’ll get more powerful results by using the later? Also, what do you make of this study: ? What is the difference in energy deliver; and should I used it the same way ie 4cm distance at 3-4 minutes? Thanks again.

    • Joe says:

      It’s an interesting study, showing better results on the testes of rats with high dose red than high dose near infrared. The near infrared seems to cause heat damage while the red is still beneficial.
      They are using a really high dose for some reason (360j/cm2) with a high power laser. I feel sorry for the poor rats and their tiny testes. This dose might be ok for human testes, but is so high for rats and probably causes overheating. Since the near infrared is more penetrative, this explains the difference in effects.
      I think a more reasonable dose of red will provide even better results, or even just using something to prevent the testes heating up, like a desk fan or something at the same time.
      I don’t think you should try to extrapolate human doses based on this rat study. All that you can conclude is that extreme high dose red is safer than extremely high dose NIR down there.

  14. John says:

    I tried this and my total testosterone went DOWN 15%. Here’s the details of my experiment:

    Light: 26W Deep Red 660nm LED Light
    Exposure time: 6 minutes/Session with 3 Sessions/Day (Morning/Afternoon/Evening)
    Exposure method: I allowed the surface of the lamp to press gently against my scrotum for 30 second increments. 30 seconds in the front, 30 seconds on the left side, 30 seconds on the right side, 30 seconds on the bottom, and 30 seconds on the back side. That’s 3 minutes, so repeat twice. I kept with this sequence for all 4 days, but I did more research and it seems like the Leydig cells are best illuminated from the front and sides of the scrotum, so there may be room for optimization.

    Total testosterone test
    Monday 7:30am (before I started light exposure): 906 ng/dL (nice and high without light)
    Friday 7:30am (after 4 days of light exposure): 772 ng/dL (15% LOWER!!!!)

    35 year old Caucasian American Male
    Good health, ~16% body fat (I’d like it to be 10%)
    Exercise daily
    Why four days? Because according to the rats study, day 4 saw a huge spike in testosterone:
    I did have a slight cold during the four days and work was slightly more intense than usual, but I felt like I handled the work intensity much better (like it was a challenge to be conquered)

    For the first couple days, I felt a slight nausea in the morning, however, I also felt a subtle confidence/positive outlook and a little more pep in my step. I did not ejaculate during the 4 days, but I have continued the light and had sex since then. I seemed to notice increased sexual performance.

    Could it be an adjustment period? Other factors? Wrong wavelength (I noticed on this site there is a blended light of 610nm, 630nm, 660nm) maybe that stimulates the process better? Maybe during the first week the results aren’t reflected in the labs?

    Again, I can’t emphasize this enough. I did feel better more energy, more confident outlook, better response to stress, better sexual performance, but my labs did not match. Sure, there could be a “placebo effect”, but my total testosterone did change 15% which seems like a lot in a short time.

    • Joe says:

      While I admire your determination and scientific experimentation, you’re definitely doing too much. As mentioned above in this post, heat is detrimental to testicular function. So 18 minutes of a light pressed onto your testes per day is not a good idea. I’ve heard of people trying to use heat lamp bulbs down there and complaining it didn’t work. Your application was not as extreme as a heat lamp but same sort of problem.
      Guessing a dose blindly, even with an appropriate light device, is also not a good idea. You should measure the light intensity of a light before therapy. 2 minutes total per day from a light at about 50mW/cm2 intensity is more appropriate. It is a good idea to stop before you notice any real hyperthermia in the skin of the scrotum at least.
      Day to day variations in testosterone can be up to 40% in studies I’ve seen (Ahokoski et al. 1998 – Biological day-to-day variation and daytime changes of testosterone, follitropin, lutropin and oestradiol-17beta in healthy men.) so a 15% drop between 2 tests is not significant.

      • John says:

        Thanks for the reply. I will cut back on the total time, but just to note, my testicles never got too hot because I moved the light around every 30 seconds and spread the time out over 3 sessions.

        It seems testing is a big part of the challenge:

        “Problems within laboratories make it impossible to compare results. “We sometimes see 30%-plus differences in testosterone levels obtained on the same day from the same patient but measured in 2 different laboratories,” says Dr Paduch.”

        “Testosterone levels can be decreased 25% within 30 minutes of stress and elevation in stress hormones like cortisol,” emphasizes Dr Paduch.”

        “Approximately 44% of total testosterone (TT) is bound to SHBG, but bound T is not bioavailable. Factors that increase SHBG, like aging, may lead to increased TT levels in men who are nonetheless hypogonadal because bioavailable T levels are below normal.”

        • Joe says:

          While personal testing will never be scientifically conclusive, the heat is definitely the most likely issue in this case. The average temperature of the scrotum/testes is about 1-5 degrees Celsius lower than normal body temperature. Even a temperature increase of 1 degree (raising it to normal body temperature) hinders sperm/testosterone production. So if a 1 degree increase is too hot, there’s no doubt that using your light, pressed onto the skin for 6 mins per session, even moving around in different positions, had that effect if not much more.

          • John says:

            So which of your products do you recommend for increasing testosterone? Red Light Mini? Combo (Red/Infrared Mini)? And what dosing/angles?

        • Dan Konig says:

          Might be a dumb question but how do you measure light intensity/density and wavelength? I’m not sure I understand how angles factor in. Got an info on that?

          • Joe says:

            You measure light intensity with an irradiance meter. Wavelength with a spectrometer.
            The angle that light comes out of a light source is one of the main factors in determining how the power density changes by distance. Wide beam angles, such as over 60 degrees, make the power density weaken very soon. Narrow beam angles like 30 degrees keep the power density strong over long distances.

  15. Luis says:

    Is it possible to use the full body laser to take out moles, melanoma skin cases, also I am very interested on the hair restoration. Your comment on this matter is greatly appreciated.

    • Joe says:

      Hi Luis,

      I don’t know about the melanoma issue. It might have some effects on new moles but I can’t see it removing long term moles.
      It definitely has potential to help with hair restoration.

  16. Alex says:

    Hey! Great article. Good to know that i was about to burn my balls 🙂
    I’ve got one question. In one of your answers to a comment you said that it takes 50+ watts to penetrate the skin “ lower intensity lights (<50 watts for LEDs) won't even penetrate the surface layer of skin" . So i'm a bit confused cause some of your recommended light devices (the mini ones) only have a light consumption of about 10-20 watts.
    Do i miss something or how do they work then?
    Kind regards, Alex

    • Joe says:

      Hi Alex,
      Sorry, that was outdated information based on our earlier models. The main factor in penetration is actually power density, which you measure in mW/cm2 – milliwatts per centimeter squared.
      For deeper penetration you want to use the lights close enough to give at least 50mW/cm2, and even 100/200mW/cm. For the testes you don’t need that high of a power density. I think 20-50mW/cm2 is fine.

  17. Tom says:

    Does testicular motion, or lack thereof, reveal anything useful about the light intensity being used?

    • Joe says:

      Hi Tom, I don’t think so, but I don’t know. The slightest touch or repositioning of the body will induce testicular movement, so it is more likely related to that than the light.

  18. Bo says:

    Good guide you have made!
    I have just one question.
    Can I place my led device (660nm) directly on my testicles or should it be at a distance of 1 – 2 inches?
    I read another guide saying there should be a distance of 1 – 2 inches.?

    • Joe says:

      It’s not just the heat, but EMFs too to be concerned about. I would use a light therapy device on the testicles from as far away as possible. There’s no set distance to use them from in general, it all depends on the specifications of your device, such as power density, EMF readings, etc. Most general LED devices are not intended for light therapy, and so you can’t use them from far away while maintaining a good power density (because of the wide beam angle).

  19. Bo says:

    And ups.
    I forgot to say that an device (660nm red led) does not makes any heat only wery wery wery weak heat so weak I cant realy feel it when placing the device Directly on the testicles 🙂

    • Joe says:

      You need to know the power density of the light in mW/cm2 and need to now how that changes by distance. It is also worth checking out the EMFs by measuring in milligauss and V/M, especially for unearthed products, and how that changes by distance. I don’t know if you can or should use your devices. Perhaps they are suitable and perhaps not. You can’t know without the relevant specifications.
      I wouldn’t recommend blindly putting random LED devices near your testicles.

  20. Mod says:

    Hi there Joe,

    Since the 830 infrared mini emit not heat; can they be applied atop testes and for how long do you recommend using them per session?

  21. Mod says:

    Alright. Do you think it’ll be a problem if I used the 830 mini two days in a row? I plan on using it twice a week.

  22. Marcus says:

    Hi Joe,

    So I just bought the Red Light Mini. I’m already feeling results when applied to the neck area, great!!!

    What would be the guidelines for using this specific lamp for increasing testosterone ? Something like :
    Everyday, 3 minutes session at a 10 cm distance from the testes ?

    Would that be good ?

    • Joe says:

      Hi Marcus,

      If 12 J/cm2 of laser light damaged rat testicles, maybe something like 4000J/cm2 would damage human testes – a dose that would take months continuously to achieve.

      I am not sure of the average rat testicle weight compared to humans, but we definitely have larger gonads. So you can’t use a rat dose and make conclusions about humans. It’s like saying a 300 calorie diet makes rats obese, therefore us humans should eat less than 300.

      This type of study would be worrying if rats were the same size as humans, but they’re not. I guess its not obvious to you, but we humans are larger than rats and require larger doses of light (or drugs, supplements, calories, etc). A lethal dose of caffeine for a rat is just a normal cup of coffee for us. I remember once seeing a study with rats on aspirin – they basically pumped the rats stomach completely full of aspirin, and then claimed that relatively low doses (low doses by human standards) of aspirin caused stomach damage.

      These rats weigh 200g, and human males weigh about 85kg on average, so we are over 400 times heavier. We therefore need much higher doses of light relatively. Just as an elephant or horse would again require an even larger dose than humans. Same as with drugs.

      The issue in the study is likely tissue heating. The 50mW lasers are burning the rat testicles and denaturing cellular enzymes/proteins etc. Not an issue you would get if using an LED light on humans at 18J/cm2 for example. It’s just not possible to ever cause serious thermal damage with an appropriate red LED light.
      There are also various issues with the study. They seem to conflate Joules with Joules/cm2, don’t mention the power density (mW/cm2), etc. The laser could be focused to a tiny point of 5000mW/cm2+ intensity light for all we know.
      Poor rats, getting their balls burned by a laser isn’t a good way to go.

    • Joe says:

      Lumens is not a valid unit for measuring red light. Just ‘red’ in general is also not enough information.
      You need to know the exact wavelength and the power density of the light, and also how the power density changes by distance.

  23. Gene says:

    I’m skeptical of this because this type of therapy would be the easiest thing to measure. You can simply test your testosterone levels before and after therapy. I have never heard of anyone who advocates for this type of therapy to actually say how much his own testosterone increased as a result of this therapy. I suspect that it’s a very small increase if at all.

  24. M says:

    You wrote “More recent human studies support the same theory, showing potentially even more positive results compared to birds/mice, with preliminary results showing a steady, dose-dependent jump in testosterone levels.” Where is this study? I don’t see it in your list of references.

  25. Jeremy says:

    Is there a specific time of day that’s most beneficial for testosterone increases? I know testosterone levels drop for about 3 hours after each meal; would it make sense to use the red light after eating, or will that reduce the effectiveness? Also, any excitatory effect that might want to be avoided right before going to sleep?

    • Joe says:

      I don’t know about the ideal time of day, at least I haven’t seen any studies on it, so would only be guessing.
      Red light just helps your cells to produce more energy and CO2, by removing nitric oxide (an oxygen blocker) from the mitochondria. I think using light in the morning would be the best time of day, but I don’t know for sure. There is not an excitatory effect from red light.

  26. John says:

    Hello. In reading through the comments I saw ED referenced as potentially treatable with red light therapy. Is this anecdotal or are there studies? Can you share the links? I was very familiar with the testosterone boosting benefits but not the ED related possibilities.

  27. Blake says:

    Hi there, I have been tanning my testicles everyday for a week or two and been noticing some benefits. But they are really brown, and the benefits feel like they;re dropping off. I think I’m overdoing it. They tan faster than the rest of my body. I’m trying to find the ideal time in the sun so I can get the bare minimum for benefits. Did you see anything on the length of time for exposure to sunlight?

    “More recently, studies have been done on direct sunlight exposure, firstly to the torso, which reliably increases male’s testosterone levels by anywhere from 25% to 160% depending on the person. Sunlight exposure directly to the testes though has an even more profound effect, boosting testosterone production in Leydig cells by an average of 200% – a large increase over baseline levels.”

    Do you have a link to that study? I always thought the only testicles and sunlight exposure study was the one from the 1930’s and all others since used red light or artificial UVB light not actual sunlight. Maybe there’s a mention in that study of length of time? I’m thinking 10 minutes per day on testicles, or 10 minutes every other day. I do body everyday for vitamin D (again not too long though)

  28. lorenzo says:

    dude please, i read this study:

    I was so happy to have found something to rise my testosterone, and i online bought a small led (660nm).

    but i was so excited that i could not wait, so i took a small (very small) incandescent lamp (pretty old) and i put on top of it a red socks (light red not too intense) to filter all the other wavelength and basically i thought that would be the same of a “normal” red light bulb. so i used it for like 2-3 (maybe less) hour in 2 days (1 hour the first,2 the second and maybe a little bit (10 minutes the third day), i felt no burn no heat, cause the socks was taking all the heat and i was pretty comfortable nor i felt problems after it i was just fine.

    but then, on the third say, i remembered that incandescent bulb has even nir higher wavelength (>800) and that maybe it could have pass through the socks, now I’m just too worried that i have destroyed my testis, I’m feeling some pain (really only when i think about it so it could be easily be nocebo). but i did not warm up my testis. what do you think should i go to the hospital? my testis fine at touch, but one seems harder then the other (I’m not really sure about it either)

    • Joe says:

      You really have to question where your life is heading when, one day, you find yourself shining an incandescent light bulb towards your scrotum through a red sock.
      Seriously though, don’t worry, your testes will be fine. NIR light doesn’t destroy cells. Even if you were heating your testes, they will still be fine.
      Just put the sock away, put the light bulb down. Don’t use incandescent bulbs near your testes, don’t use random LEDs near your testes.

  29. Justme says:

    I bought red device mini from you. I am confused because people say that red light led doesn’t heat. The above somebody said that he has 670nm light and he can barely know if there is any heat when he puts the light next to skin. But with this device I can feel the heat. With distance 10cm heat is very weak but still there, with 1cm it is very obvious in a second. Is that normal or is my light “broken”?

  30. Anonymous says:

    I just bought the therabulb near infrared bulb on Amazon for shining down down below. At what distance would you consider it to be safe to use?

  31. Jon says:

    35 year old male here. Somewhat active, could be more. While I haven’t done blood work, I can report very good n=1 anecdotal results shining 660 & 830 nm photons on my testicles and neck, targeting thyroid. I’m using a proper photobiomodulation device, not some random LEDs or bulbs.

    The key is not to overdo it. Once or twice a day for 3 minutes from a few cm distance does the trick. I’m doing a little more on thyroid, 5-7 minutes seems good.

    Pros: More energy and optimism and desire to do stuff. Higher sex drive, stronger orgasms and ejaculations, faster recovery time, turned on by random women.
    Cons: Borderline douchebag mode at times, quicker temper.

    Two weeks into this now. Hoping to god it’s not just placebo. We’ll see.

  32. Anonymous says:


    I have stupidly used a 100w heat lamp and cooked my testicles, I now have pain in my abdomen, any advice besides seeing a doctor?

    • Joe says:

      Sorry, we really can’t give medical advice.
      As mentioned in the article above, we strongly recommend against shining heat lamps onto the body, anywhere, especially the male scrotum.

      • Anonymous says:

        Hey there. Could one expose their testicles to red light overnight if they had a cooling mechnism to counter the negative heat effects? (ice pack or something?)

      • Sam says:

        Hey couple questions! One i have hot baths everyday. Are you saying this is bad for T? Also if one had an ice pack or some sort of cooling mechnism, t could they use a red light all night without damage from heat?

        • Laura says:

          I would assume daily hot baths to be bad for testosterone and male fertility, yes. A cool (35 degree C / 95F), almost cold bath would be better.
          I have seen studies where a cooling mechanism was used to maintain normal skin temperature, and despite the very very high dose of light used, there were only positive effects. So yes, I believe if you control for temperature you can apply very high doses with positive effects. I don’t know if an ice pack is suitable – you don’t want the skin to get too cold either.

  33. Anonymous says:


    I have done something stupid, I used a infrared heat lamp 100w for 15 mins, I have abdominal pain and sure I have fried my testicles, any advice?

  34. Mike says:

    Hi, what do you think is best for increasing T levels; the pure 660nm red light or the NIR or a combo red/NIR light? It appears that the pure red light is best for increasing T levels but I just wanted to verify. Thank you in advance.

  35. Adaptogen says:

    I have a device, claiming :
    “0 inch : > 200 mW / c㎡
    1 inch : 141 mW / c㎡
    3 inch : 45.0 mW / c㎡
    6 inch : 25 mW / c㎡”
    simultaneously using 630, 660, and 850nm wavelengths.

    Could you give a recommendation (for my rat) for duration, distance from, and frequency to use on testis for increasing testosterone production?

    Also, based on these specifications, what duration/frequency would you recommend to treat tendonitis type issues?

    Thank you kindly in advance, just the comment section of this single blog post has been a tremendous wealth of information.

    • Laura says:

      It is just a matter of overheating the testicles. A lower dose, one that avoids tissue warming, is essential for improving testicle function. Studies show that even a 1 degree temperature increase will cause harm to the testes, so it is a matter of heat, not necessarily wavelength. Wavelengths around 808nm are well proven across the body for benefits – the testes are the most temperature sensitive part of the human body.

  36. Kim says:

    Could this work for someone with Klinefelter’s syndrome? Someone I know has it, and from what I understand, he can produce sperm but it dies before it makes its way out. He’s had surgery to remove sperm for successful in vitro in the past. Could red light therapy help keep the sperm healthy and alive?

  37. Dave says:

    I’m just wondering whether there are any studies looking at Dihydrotestosterone? As I understand it Dihydrotestosterone is produced by the body from testosterone and is associated with Prostate growth and androgenic alopecia. Is there are risk of accelerating Benign Prostate Hyperplasia from using red light therapy?

    Many thanks

  38. KC says:

    What are your thoughts about red light therapy for men suffering from azoospermia (lack of sperm observed in a semen analysis)? Are there any studies/research done for it?

    • Joe says:

      No, red light is just restoring aerobic respiration (rather than anaerobic respiration) to help cells produce ATP efficiently.
      There’s no mechanism for excessive or abnormal hormone production.

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