Complete guide to light therapy dosing

guide to dosing light therapy

Light therapy, Photobiomodulation, LLLT, phototherapy, infrared therapy, red light therapy and so on, are different names for similar things – applying light in the 600nm-1000nm range to the body. Many people swear by light therapy from LEDs, while others don’t seem to notice much at all, finding better results with heat lamps or incandescents, or no results from anything.

The most common reason for this discrepancy is a lack of knowledge about dose. To be successful, you first need to know how strong your light is (at different distances), and then how long to use it for.


What is the strength of my light?
How to calculate dose
Effective doses from studies
More to learn

Medical & Healthcare Disclaimer
The information contained in this article is not intended or implicitly suggested to be an alternative for professional diagnoses, or profesionally recommended treatments & medical advice. Absolutely all of the content, including the article text itself, images, comments and other information, contained on this web page is for non-specific information purposes only. We strongly suggest that one should never ignore professional health/medical advice and we strongly suggest that one must not delay seeking a professionally recommended medical treatment because of information attained via reading this article/website. The products sold or recommended on this web site are absolutely not for the diagnosis, prevention, monitoring, treatment or alleviation of any specific disease, injury or disability.

How can I know the strength of my light?

The power density of light from any LED or laser therapy device can be tested with a ‘solar power meter’ – a product that is usually sensitive to light in the 400nm – 1100nm range – giving a reading in mW/cm² or W/m² (100W/m² = 10mW/cm²).

Power density? This is a measurement of how concentrated the light is at a given point (a.k.a. energy density, light power density, etc.). Specifically how many light photons are passing through a given area of space.

With a solar power meter and a ruler, you can measure your light power density by distance. Below are the light power density readings of three of our products at different distances:

Infrared light Device Red Light Device Red/IR combo
Distance (cm) Power Density (mw/cm²) Power Density (mw/cm²) Power Density (mw/cm²)
0 1200 1100 1000
5 500 450 600
10 200 180 450
15 100 90 200
20 70 65 100
25 45 40 85
30 35 30 70
35 20 18 55
40 18 15 40

(Power densities over about 200mw/cm² are not typically indicated for skin treatment as they are too powerful, however they can still be used for short periods to target deeper tissue. Power densities in the 500-1000+ range offer excellent penetration, useful for muscles, joints, brain tissue, etc.)

You can test any LED or laser to find out the power density at a given point. Full spectrum lights such as incandescents & heat lamps cannot be tested this way unfortunately because much of the output is not in the relevant range for light therapy, so the readings will be inflated. Lasers and LEDs give accurate readings because they only output wavelengths +/-20 of their stated wavelength.

Optimal strength range

Once you have the readings of your device, you can determine the ‘light therapy range’ or the distance from which it needs to be applied to give an appropriate power density. This tends to be in the 10 – 200mW/cm² range. Vary the strength by varying the distance you apply light from.

Here is the therapy range of our Red Light Device for example:

red light device effective range
RLM Red Light Device showing effective range between 10cm & 35cm
infrared mini light therapy range
Therapy range of the infrared mini 830 device


How to calculate light therapy dose

Light therapy dose is calculated with this formula:

Power Density x Time = Dose

Fortunately, most recent studies use standardised units to describe their protocol:

  • Power Density in mW/cm² (milliwatts per centimeter squared)
  • Time in s (seconds)
  • Dose in J/cm² (Joules per centimeter squared)

For light therapy at home, power density is therefore the main thing you need to know – if you don’t know it, you won’t be able to know how long to apply your device for to achieve a certain dose. It is simply a measure of how strong the light intensity is (or how many photons are in an area of space).

With angled output LEDs, the light is spreading out as it moves, covering a wider and wider area. This means relative light intensity at any given point gets weaker as distance from source increases. Differences in beam angles on LEDs also affects the power density. For example a 3w/10° LED will project light power density further than a 3w/120° LED, which will project weaker light over a larger area.

Light therapy studies tend to use power densities of ~10mW/cm² up to a max ~200mW/cm².
Dose is simply telling you how long that power density was applied for. Higher light intensity means less application time is required:

5mW/cm² applied for 200 seconds gives 1J/cm².
20mW/cm² applied for 50 seconds gives 1J/cm².
100mW/cm² applied for 10 seconds gives 1J/cm².

These units of mW/cm² and seconds give a result in mJ/cm² – just multiply that by 0.001 to get in J/cm². The full formula, taking into account standard units is therefore:

Dose = Power Density x Time x 0.001

 What dose should I aim for?

dose-responseNow that you can calculate what dose you are getting, you need to know what dose is actually effective. Most review articles and educational material tends to claim a dose in the range of 0.1J/cm² to 6J/cm² is optimal for cells, with less doing nothing and much more cancelling out the benefits.

However, some studies find positive results in much higher ranges, such as 20J/cm², 70J/cm², and even as high as 700J/cm². It’s possible that a deeper systemic effect is seen at the higher doses, depending on how much energy is applied in total to the body. It could also be that the higher dose is effective because the light penetrates deeper. Getting a dose of 1J/cm² in the top layer of skin will only take seconds. Getting a dose of 1J/cm² in deep muscle tissue could take 1000 times as long, requiring 1000J/cm²+ on the skin above.

Doses shown to be effective in different areas:

Area being treated Effective Dose [w/ref] J/cm² Red Light Device @ 8cm Infrared Light Device @ 10cm
Acne 5 to 96 [10] 3 mins 5 mins
Back Pain 40 to 120 [14] 7+ mins
Braces 8 to 64 [12] 3 mins 3 mins
Braces Pain 60 [7] 5 mins 5 mins
Brain 60 [11] 5+ mins
Cellulitis 60 [1] 5 mins
Depression 60 [11] 5+ mins
Dermatitis 60 [1-2] 5 mins
Hair loss 67 [3-4] 6 mins
Joint Pain 40 to 120 [14] 7+ mins
Muscle 80 [13] 7+ mins
Oral candida 5 to 20 [8] 2 mins 3 mins
rosacea 60 [1-2] 5 mins
Scars 27 [2] 2 mins
Skin 0.1-50 [2] 2 mins
Thyroid 38-707 [5-6] 10 mins 6+ mins
Wound healing 60 [9] 5 mins 5 mins

Distance of the light source is crucially important here, as it determines the light power density hitting the skin. For example, using the Red Light Device at 25cm instead of 10cm would increase the application time required but cover a larger area of skin. There’s nothing wrong with using it from further away, just be sure to compensate by increasing application time. The session times mentioned above are estimates and loosely take into account wavelength penetration rates.

Calculating how long a session

Now you should know your light’s power density (varying by distance) and the dose you want. Use the formula below to calculate how many seconds you need to apply your light for:

Time = Dose ÷ (Power density x 0.001)

Time in seconds, dose in J/cm² and power density in mW/cm²

Is there more to light therapy dosing?

While the information laid out here is adequate to measure dose and calculate application time for general use, light therapy dosing is a much more complicated matter, scientifically.

  • J/cm² is how everyone measures dose now, however, the body is 3 dimensional. Dose can also be measured in J/cm³, which is how much energy is applied to a volume of cells, rather than just applied the surface area of skin.
  • Is J/cm² (or ³) even a good way to measure dose? A 1 J/cm² dose can be applied to 5cm² of skin, while the same 1 J/cm² dose could be applied to 50cm² of skin. The dose per area of skin is the same (1J & 1J) in each case, but the total energy applied (5J vs 50J) is vastly different, potentially leading to different systemic outcomes.
  • Different strengths of light can have different effects. We know that the following strength and time combinations give the same total dose, but the results wouldn’t necessarily be the same in studies:
    • 2mW/cm² x 500secs = 1J/cm²
    • 500mW/cm² x 2secs = 1J/cm²
  • Session frequency. How often should sessions of ideal doses be applied? This may be different for different issues. Somewhere between 2x per week and 14x per week is shown effective in studies.



Using the right dose is key to get the most out of light therapy. Higher doses are required on the skin in order to stimulate deeper tissue. To calculate dose for yourself, with any device, you need to:

  • Figure out your light’s power density (in mW/cm²) by measuring it at different distances with a solar power meter.
    • If you have one of our products, use the table above.
  • Calculate dose with the formula: Power Density x Time = Dose
  • Aim for dosing protocols (strength, session time, dose, frequency) that have been proven effective in relevant light therapy studies.
    • We have listed some examples above.
    • For general use and maintenance, keep between 1 and 60J/cm²
  • Repeat sessions anywhere from twice a week to twice a day or more.



  1. Is light-emitting diode phototherapy (LED-LLLT) really effective? WS Kim et al. 2011.
  2. Low-level laser (light) therapy (LLLT) in skin: stimulating, healing, restoring. P Avci et al. ‎2013 .
  3. The growth of human scalp hair mediated by visible red light laser and LED sources in males. RJ Lanzafame. 2013.
  4. The growth of human scalp hair in females using visible red light laser and LED sources. RJ Lanzafame. 2014
  5. Low-level laser therapy in chronic autoimmune thyroiditis: a pilot study. DB Höfling et al. 2010.
  6. Low-level laser in the treatment of patients with hypothyroidism induced by chronic autoimmune thyroiditis: a randomized, placebo-controlled clinical trial. DB Höfling et al. 2013.
  7. Efficiency of low-level laser therapy in reducing pain induced by orthodontic forces. AA Bicakci. 2012.
  8. In Vitro effect of low-level laser therapy on typical oral microbial biofilms. FG Basso et al. 2011
  9. 830 nm light-emitting diode low level light therapy (LED-LLLT) enhances wound healing: a preliminary study. PK Min et al. 2013.
  10. Combination blue (415 nm) and red (633 nm) LED phototherapy in the treatment of mild to severe acne vulgaris. DJ Goldberg et al. 2006.
  11. Psychological benefits 2 and 4 weeks after a single treatment with near infrared light to the forehead: a pilot study of 10 patients with major depression and anxiety. F Schiffer et al. ‎2009.
  12. The effect of low-level laser therapy during orthodontic movement: a preliminary study. M Youssef et al. ‎2008.
  13. Does Phototherapy Enhance Skeletal Muscle Contractile Function and Postexercise Recovery? A Systematic Review. Borsa et al. 2013.
  14. Meta-Analysis of Pain Relief Effects by Laser Irradiation on Joint Areas. Ho Jang et al. 2012.

118 thoughts on “Complete guide to light therapy dosing

  1. Joshua Forter says:

    So are these daily recommendations? For example…for thyroid…I would use the IR 6+ minutes a day EVERYDAY? Thanks.

    • Joe says:

      You could do. I suspect the optimal protocol is different for everyone. I suggest experimenting with session frequency between 2x per week and 14x per week. and perhaps for longer session times.

  2. Janis Bell says:

    Do you have any information on using the lights with arthritis? Guessing under joint pain, but it’s a little different as my husbands thumbs are all swollen and puffy too.

  3. Peter Martinez says:

    Very comprehensive yet informative breakdown. There is a lot of confusion about this topic out there. It’s nice to see someone package it for us so nicely. Thanks

    • Joe says:

      My understanding is that the ideal wavelength for acne treatment is 415nm and that 415nm/blue only lights are somewhat effective. There seems to be a synergy between blue and red though, and combination lights/treatment are considered superior. It makes sense if you think about it – blue will kill bacteria, but also stress your cells – blue combined with red will still kill bacteria, but your cells will have protection. Red only lights have proven effectiveness against acne too. Infrared doesn’t seem as effective as red for acne.

      Blue-only –
      Red-only –
      Combination blue-red – &
      Combination blue-infrared –
      Blue-only vs. combination blue-red –

    • Joe says:

      It depends what dose you want to aim for. For hair health I’ve seen 1.5J/cm² all the way up to 70J/cm² in studies. With your device directly on the scalp, that’s anywhere from 12 seconds up to 10 minutes.
      You can use it a few cm above the scalp if you want, I suppose the wavelengths will be more evenly blended like that. You’ll just need a longer session time to get the same dose. 5cm away = double the time required. 20cm away = 4x time required.

      • Beverly says:

        I need to know if tan center red light bed with 330 mn. Suggested daily 15 min sessions will give me all available health benefits..very cheap but need benefits

        • Joe says:

          Do you mean 630nm rather than 330nm?
          If so then it is a good wavelength. The ideal time for a session depends entirely on the power density (light intensity) hitting your skin, so I can’t say if 15 minutes is a good session in that tan center bed.

  4. Diego says:

    Great article!! I’ve read that red light can contributes too to photoaging, and there are some sunscreens that protect from this range too, like vitamin c based serums, is this correct?

    • Joe says:

      I do not believe so. Red is protective against photoaging. Strong sources of longer infrared like heat lamps and sunlight might contribute to photoaging in large doses. For red to contribute to photoaging, you’d literally have to burn your skin with it. I don’t know about the vitamin C based serums, but I know sunscreen producers are looking for ways to block the longer infrared rays in addition to the UV.

  5. beth says:

    Anyone know where I can find the info on hz and nm for red light therapy lipo machines? Considering buying one but would like know more about how and why they work first.

  6. PK says:

    Can use red and blue LEDs that are designed for plants that are at the right wavelengths and calculate the dose using the formulas from your post.

    • Joe says:

      Blue LEDs will be problematic as they damage mitochondrial function. Otherwise though yes, as long as you know the power density at a certain distance you can calculate a dose.

  7. PK says:

    Can I use a Lux meter instead of a solar power meter and convert to W/CM2? I can get an app for my iPhone and do this. I know that the iPhone has an IR filter but the specs say it is set for a 800nm cutoff.

    • Joe says:

      I’m not sure about that. If you can get a reading that seems reasonable then go for it. Any sort of measure of light intensity would work, provided you can convert it to mW/cm2 (and you know the wavelengths are in the 600-950nm range only). Lux is mainly for measuring white visible light, so it won’t necessarily show any reading for infrared units.

    • kelly says:

      What app are you using? (And have your indeed found it suffices for the purpose of measuring the light for determining potential bio-therapeutic effects?

  8. William says:

    I’ve been experimenting with placing the infrared and ref light very close to my mouth (~2 inches) for a minute or two, to give my teeth through the gums a good dose.

    How long do you think it would take for the skin or eyes to be hurt from heat damage at this distance?

    • Joe says:

      Hi James,
      I don’t know if there are any good human studies to conclude a dose recommendation for that. I think just a couple of minutes does the job fairly well with most of our devices.

  9. Julia says:

    In your last table (“Doses shown to be effective in different areas”) you list columns for RED LIGHT DEVICE at 10CM and INFRARED LIGHT DEVICE at 0CM
    However, in the chart for power density at various distances, it lists that only the RED/IR COMBO can be used at 0CM – both the RED LIGHT and INFRARED LIGHT devices list they are “out of the therapy range” (too strong) at 0 or 5 cm – please clarify if the column for that last table (doses shown to be effective) at 0CM is actually meant to be the RED/IR COMBO at 0CM

    I am considering buying your product but want to know what I’m looking at in these dose tables.

    • Joe says:

      Hi Julia,
      That table was out of date. I forgot to update it. The combo light and the infrared light models have changed since then. I have updated the tables for you now.

  10. Anthony says:

    Do you have Power Density vs Distance data for the Mini Devices? This would help determine the dose applied. Also, is there a solar power meter that you could recommend?

    • Joe says:

      Hi Anthony, I will add some charts for the mini devices.
      For the solar power meter, the Tenmars brand/range works well. Just be sure to get one that measures up to 200mW/cm² (2000W/m²) or higher.

    • Joe says:

      I’m not sure on the specifics but you would want a high dose for deeper tissue. Probably at least 50J/cm2 or maybe even upwards of 100J/cm2 or more.

  11. Ralph says:

    Could someone explain this to me: I don’t understand the dose. It is quoted from the study in your note n.4 on hairloss.

    “Patients treated at home every other day × 16 weeks (60 treatments, 67 J/cm2 irradiance/25 minute treatment, 2.9 J dose)”,

    Is it 2,9J per session of 25 minutes?
    or It is 67J per session of 25 minutes?

    I need help for that. Something is not clear in the equation.

    • Joe says:

      Hey Ralph, yeah this is a common issue between studies – that studies don’t use all the same descriptors for the same thing. The total energy applied is measured in ‘J’, but it’s not very useful because you don’t know over how large an area that is applied.
      The J/cm2 measurement is what you need to look at and that’s what I would consider to be the dose. So they are applying a 67 J/cm2 dose over 25 minutes. Use the formulas above and that gives the power density / light intensity hitting the skin is about 45 mW/cm2. So you can replicate that by using our Red Light Device from about 24cm distance and using for 25 minutes.

  12. Seppe says:

    Hi Joe, great info-page, nice work!
    I was wondering though if the energy-dose in J/cm² is the main effect-determining factor as you also claim that there is a limited effective power-density (mW/cm²) range for red/IR Phototherapy? As an example, can it be that the biological effect of day 1J/cm² is different between treatment A: 10mw/cm² x 100s and treatment B: 100mW/cm² x 10s? Parameters in both treatments are within the Low-Level Light Therapy acceptable range. In other words, is there evidence for other limiting factors (e.g. light-in tissue penetration depth or cellular photo-acceptor quantum yield) that could be important for determinig the optimal therapeutic power-density and irradiation time? In photodynamic therapy, this is the case (photosensitizer concentration, local oxygen availability & consumption rate). Thanks for sharing your view on this!

    • Joe says:

      Hey Seppe,
      Yes I think you are right. What we have laid out in this post is sort of the scientific consensus, but not the whole picture, and I think the standard guidelines for power density range and doses will change in future.
      I think there are different effects to different power densities, such as greater penetration potential.
      I don’t know if dose in J/cm² is the best way to determine effect and the effective dose does of course vary by individual depending on skin colour and other factors anyway.
      The J/cm² model doesn’t take into account the total energy input into the body which is think is significant.
      At the moment, I personally just tend to use red lights for the skin, (near)infrared for anything deeper. I tend to keep the light at a range of 200mW/cm² intensity for just a few minutes for general skin, and up to 10 mins or more for deeper issues. If I use them further away I will go up to 20 mins or more exposure, without really thinking about calculating a dose.

      • Seppe says:

        Dear Joe,
        Thank you for your ultrafast and honest reply. I beleive you are right and that the optimal doses are very variable between wavelengths, indications and the population. Luckily there is a broad effective therapeutic window and there is actually nothing that can go wrong… Thanks!

  13. Halid Muhamad says:

    Hai, Joe.

    Do you have a PDF Version of this journal? I really need this article for my thesis as my reference. if you dont mind, please email it to me.

    thank you so much, joe.

  14. Todd says:

    Hello there,
    Will you have a chart for the Mini Devices? Very curious of how they compare to the higher priced COB devices with cooling fans. Will the Red Light Mini 670 be enough for the testicles (from what I’ve read it appears to be so)? I’d like to minimize time spent with a device between my legs, but would like to save a little cash if the Mini is all I’ll need (overkill for higher power devices?). Can I press the Mini 670 directly against “my boys” or would having some distance make the light spread a little better (the COB may likely be less of a concern)? Seriously considering the new higher power COB Red Light Device for $199…the picture of it turned on seems to show a powerful “beam” with the new lens. I would like to see a “side by side” of how the two different lens of the Red Light Devices project. You seen to have an “older model” with a reflector and nothing showing the newer one (flatter lens) in use. I would love to see this. Maybe a “side by side” of all the Red Devices? Sorry for all the questions. Love your website and dedication to providing quality devices at affordable prices.

    • Joe says:

      Hi Todd,
      Thanks for the comments. The red mini devices are definitely sufficient for something like testicular light therapy, only needing a couple of minutes if you use them fairly close (5-10cm). If you press them right to the skin, the power density is a bit high and like you said the light is not evenly spread out. I will add the charts for the mini devices. The power density by distance is mentioned on the product pages. It is usually better at long distances than the more powerful lights, just covers a smaller area.
      The larger devices are all still suitable too. They’re not overkill as such, they just cover a wider area, so you’ll be hitting the balls but also the skin nearby on the groin/legs/stomach/etc.

    • Joe says:

      It depends entirely on what light you’re using, or more specifically what power density of light is coming out of it. If you have 100mW/cm2 of light intensity, I would use it for at least 5 minutes throughout the day, you can go up to 30 minutes though. It’s best to experiment a bit.
      I think near-infrared light will be preferable to red if the candida is deeper inside the vagina.

  15. Glenn says:

    Prior to finding your page I purchased a 135w ufo grow light which I have painstakingly replaced all of the 3w epileds with red leds of 630nm and 660nm. I am trying to work out the dosage for rosacea. I don’t have a power meter but have measured 3000 lumen’s @ 60cm and 30000 @ 30cm. I have been trying to convert to j/cm2 but not having any luck and chance you may be able to help?

    • Joe says:

      You can’t convert a light intensity measurement (lumens) to dose (J/cm2) directly, as dose is a measure of light intensity x time.
      First you need to figure out how to convert your lumens measurement into the appropriate light intensity measurement – mW/cm2. To do that, you need to know over what area that lumens measurement is. Is it lumens per meter, or lumens per centimeter, etc?
      It will be even more complicated though as the wavelength affects the conversion from lumens to other metrics. Lumens is a measure of white light mainly, not ideal for measuring narrowband red.
      UFO type lights have the LEDs quite widely spaced out. If the beam angle on your LEDs is over about 45 degrees, the power density is bound to be weak unless you press it close to the skin.

    • Joe says:

      I think a higher dose of near-infrared (more penetrative than red) will be useful, as you are trying to target the cells deeper in the ear and nearby in the head. I would suggest at least 60 J/cm2 pointing directly on the ear but higher doses may be better.

  16. jim says:

    It is my understanding that you need an IR meter to properly measure IR light. Solar meters are calibrated for full spectrum sunlight. I am not sure that they are accurate for single wavelength red light either.

    • Joe says:

      Hi Jim,
      Sure, you are right. There is a small degree of inaccuracy. If you need the best possible accuracy for a scientific study or something, there are more accurate meters to measure power density (although they are much more expensive). Something like a Color LED light meter would be better for measuring the red wavelengths and the IR meter like you mentioned for near-infrared.

  17. Mod says:

    Hey Jon,

    I noticed the lamp heats up at 10 minutes. I am concerned about chemicals released in the air. Specifically, bromine. Do these lamps give off bromine?

  18. Mod says:

    Well, it is my understanding that when heat reacts with painted metal and plastic; bromine is released in ino the air. There is a metaly smell when the lamp heats up. I think I’ll use the infrared instead the led. Thank you so much Joe.

    • Joe says:

      The only part of the lamps that gets hot after a while is the unpainted aluminium heat sink inside. There are no hazardous chemicals involved in the paint or anywhere else on any products.

  19. Jan says:

    I like the combo full body product but will this be sufficient for targeted areas as in thyroid or say, thumb joint issues?

    • Joe says:

      Yes of course. To use it for any sort of deeper targeted issue you just need to use it from a closer distance.

  20. Shawna says:

    Hi I have recently started red light therapy at a tanning salon but I don’t trust that they even know what the wavelength is or the density or anything so I’m not sure if it’s even safe. They put the red bulbs in a lay down tanning bed so how do I know if I’m not too close etc.. or how long to go. I got a head ache after 20 mins which was my first time and I had to double up on towels on my eyes I’m extremely sensitive to the light but I really want the benefits now I’m confused ! Please help:)

    • Joe says:

      I wouldn’t expect your average salon to know much about wavelength or power density. There’s quite a steep learning curve on the technical aspects of light therapy. I’m not sure about the red bulbs used in those tanning beds. They don’t seem to be studied at all by researchers. It makes sense for now to stick with LEDs or low level lasers.
      Getting a headache after your first full body treatment isn’t necessarily a bad thing. It’s probably a sign that you had quite a lot of Nitric Oxide in your mitochondria, and it was all displaced into the blood. This would cause quite a bit of vasodilation of blood vessels and thus a headache. Next time it will be less severe or even gone.
      Your eyes will adjust to the bright red light after a few sessions and it will even be beneficial for them, improving general vision and preventing AMD/cataracts/etc. If you are very sensitive, you should use near infrared light on the face, rather than red (since near infrared is invisible and doesn’t overstimulate the eyes). You could use something like this for full body treatment – – having the near infrared panel in front of your face and the red panels on the body.

  21. oliviaclymer says:

    I am currently in red light therapy using the pods at the nearest clinic–the bulbs are 680 and 860. If I pick appliances here, should I just go with the closest wattage and expect the same effect if dosed properly? (I am getting that the bulbs being used in the pod are specific to that set up and not necessarily exactly what I’d need to do this at home…)

    • Joe says:

      Hi Olivia,
      Yes the effects should be similar if you have similar wavelengths, similar power and surface area coverage and use for a similar time.
      The wattage of a device isn’t important as such, but the power output measured in mW/cm2 is more important. The problem is that most traditional (non-LED) type bulbs are very inefficient electrically, so the stated watt consumption does not provide a good comparison.

  22. David says:

    Thank you for this extraordinarily helpful explanation of dosage and light therapy. I am working with a newly acquired red 660 nm led panel and I am trying to work out the power density. I have a PAR meter that reads 345 micro mols at 15cm. Using the formula 119.708/wavelength nm = watts square meter/micro mols/square meter/sec, I get 62.6 watts/ sq.meter. I then divide by 10,000 (1 sq.meter = 10,000 to get 6.26 milwatts per Is that correct? If not, would you please help me find what the correct answer is? Thanks for your help and for all the great information on your site. …david…

  23. Jana says:

    What is the concensus regarding the use of sunlight for light therapy? Direct sunlight is about 0.1 W/cm2 in full spectrum, with about 1/10 to 1/3 of that in the therapeutic wavelength bands. The typical therapeutic dose of 60 J/cm2 would thus be obtained in 2000-6000 seconds. So sitting next to the window for an hour should do it, right? The glass filters out most of the UV and is transparent to IR.

    • Joe says:

      Sunlight in the morning or evening is the best, with more of it being red/NIR. Strength of light otherwise depends on location and time of year.
      I think you can get about 30mW/cm2 of light intensity of the relevant wavelengths from midday sunlight in the southern USA in summer. Only about half of this will be really at/near the peak wavelengths. An even smaller amount will be the more penetrative near infrared wavelengths.
      It’s not the same either way though. The heating of the skin cells from sunlight can lead to photoaging over time. The relative lack of strength of near infrared around 800nm means deeper penetration won’t be possible with sunlight.
      On the plus side, sunlight has some other benefits from the UV.

  24. Sean says:

    For treatment times, if I did 100J/cm2 on the back, 60J on the head, 38J on the thyroid, and 50J on the chest, etc in one day, would this add up to an overdose (through blood) or because different areas where used it’d be okay?

    • Joe says:

      No, don’t worry. That’s fine. You can’t overdose through the blood. Using light therapy like you suggest is a good way to do it. Applying large amounts of total energy to the body via different sites will give positive results. ‘Overdosing’ is only a single cell issue, and only relevant to the top layer of skin cells in humans. The problem with it is mainly the inadvertent heat build-up, rather than any negative photon-tissue reaction, as skin cells (or sperm cells or other single cell) don’t function well over 46 degrees C.

  25. Sean says:

    Your graph says optimal for cells is 0.1-6J/cm2 and overdose is ~70J/cm2. So if you where to target, say the thyroid with 100J/cm2, wouldn’t you be overdosing the skin cells on top?

    • Joe says:

      Yes. There’s no avoiding the skin overdosing when targeting deeper tissue.
      You could split the 100J/cm2 dose throughout the day if you are particularly concerned. The negative effects of ‘overdosing’ is mainly down to the heat build-up over time in my opinion.

  26. Sean says:

    If your device is 200mW/cm2 @0cm and 20mW/cm2 @60cm then would 30cm = 110mW/cm2 or is it exponential so 30cm = ~50mW/cm2.

  27. Mary says:

    Hi there! I was wondering if you’d be able to help me figure this out as I’m not sure I know what I’m doing. A friend ordered this for me to use for anti aging purposes. Can you help me understand the proper dosing with this model? Many thanks in advance!

    Yescom 225 Red LEDs Grow Light Panel Hydroponics Indoor Garden Room Tent Ultrathin Plant Lamp

    • Joe says:

      Hi Mary,
      I’ve tested something similar to this model before and it measured at about 5 mW/cm2 – and that’s at close range. So it is not suitable for light therapy.
      The wide positioning of the LEDs, wide beam angle and so on that you find in these type of ‘grow light’ devices in general make them inappropriate for light therapy.

  28. dale says:

    I am very confused , about which red lite handheld laser is best for me to use I have a tendlite now I don’t know if 600 or 1100 is best for me to use on my back and shoulders and which laser is rated best for deeper penetration. which one is adjustable to cover a wider area or to pin point and area ?

  29. Haig Tutundjian says:

    Hey Joe:

    I’ve got your Red-IR Combo Mini unit; & I’d like to try it on an abdominal hernia which I noticed coming on about a month and a half ago.
    Since this unit’s only 6 of 12 diodes are IR (for muscular penetration) I’m cutting the Power Density in half from 200-100mW/ (@ 5cm.) to come up with 13 min. & 20secs.
    13:20 = 80 / (100 x 0.001)

    Also, I’m aiming the IR diodes to cover the affected area.
    Is my assumption correct?

    I thank you in advance for your help.


    • Joe says:

      Hi Haig,
      The beams of light from the 12 LED lenses do start to converge around 5cm, but not fully. So I don’t think you should cut the power density in half at that distance if you are aiming the IR LEDS on one spot. Maybe trim off 20% of the power density if you are going to calculate it like that. The red light will still be useful though, even if it has less penetration potential. Studies show systemic changes in hormones and reductions in inflammatory markers and such from exposure anywhere on the body.
      Otherwise yes, it sounds like you are doing it right. Aiming the IR light, especially the non-visible 830nm LEDs, will give the best penetration. You might consider something more suitable for better effects:

  30. Gary says:

    Hi Joe,

    Can you recommend a starter light for someone who would like to use it for a bit of everything?!

    I would like to use it for knee crepitus, no pain just creaky knees. I would also like to use it for wound healing and general skin health and muscle recovery after exercise (or preventative as it seems to state on your website), maybe even hair growth.
    A big ask for just one device, I know. But if you could point out one product that work on all of these, using various distances, I would really appreciate it.

    Thanks in advance for your help.


    • Joe says:

      This is a good choice, with a broad range of wavelengths, useful for skin and deeper tissue. More importantly, it is quite powerful, which aids the penetration for things like muscles.
      You would use it close to the skin to target the deeper tissue, and use it from further away to cover a wider area of skin with appropriate light intensity.

      • Di says:

        Do you have any information re using light therapies for kidne problems.?
        Have bought redlight mini combo for other reasons.

        • Joe says:

          I have seen mostly animal studies on the kidneys, for things like preventing fibrosis and reducing oxidative stress, so it seems useful.
          I don’t recall anyone ever mentioning that they used the Combo Mini specifically for that, but it is worth a try. Just use it over the lower back kidney area for 5-10 minutes or more.

  31. Lyle says:

    I have a p300 660nm light. Is that the optimum wave length for deep tissue penetration.? I want to use the light for wound/injury healing. I have read that 880nm is better and I can get a light that is a mix of the two wavelengths. Also , how close should hold the light to my skin and how far does the light penetrate?

    Thank You

    • Joe says:

      Hi Lyle,
      No, it is not the ideal wavelength for penetration. 880nm is also not ideal, for that or for wound healing. How close you use the light depends on what the power density of that light is at different distances. How far the light penetrates in sufficient intensity depends on the wavelength(s) and the power density, and also various other more minor factors.

      • Chris says:

        good question! I’m also looking for something to treat the inner ear (acoustic trauma). So you would definitely choose the IR wavelenghts for the inner ear? I read somewhere that the “more red” wavelengths have more healing potential, is that true?
        Do you think the 830 Mini also has enough power to make it to the inner ear?

        Can the “big” 830 Device be operated safely in a close distance to the ear? Is it loud when turned on?
        Thank you!

        • Joe says:

          Yes, definitely the near infrared range around 800nm for deeper tissue. Even if ‘more red’ wavelengths were better for healing (which they aren’t), they simply don’t penetrate as deep as the near infrared.
          830 Mini still goes up to and over 200mW/cm2 irradiance, so plenty of power output and penetration.
          You can use the big 830 device pressed to the skin/ear. It is not loud. Just a quiet fan.

  32. Dave says:

    Have you seen any research on existing keloid scar reduction or elimination with red light therapy? I found one reference but it talked about red light therapy immediately following a dematological operation and got good results, but wasn’t sure about an existing scar that’s been around for years. Thanks!

  33. Shari Douglass says:

    I have a lamp that is 12W Deep Red 660nm LED, that I am wanting use for facial and anti-aging purposes. It produces The lamp produces approximately 250W/M2 @1 foot. [25mW/cm2 @1 foot]. Although you have been very detailed in your description and equations, I still think I am not calculating my time incorrectly. I was wondering if you would be so kind to give me the optimal time of exposure and how often I should use the lamp. I was under the impression that 4-6 Jules was optimal per exposure, but I don’t know if you have come to the same consensus. Thank you for your help!

  34. Kate says:

    I have just ordered a couple of mini lamps. I was wondering if you could recommend a material to block the light rays so I can specifically target a healing wound. I also have rosacea and wish to shield non-affected skin whilst targetting my problem areas.

    • Joe says:

      I can’t remember that device specifically. As long as a device has a wavelength output in the 600-900nm range, it will have some good effect. It should also have between 20 and 100 mW/cm2 power density output hitting your skin for wrinkles.

    • jdblack6 says:

      I don’t know if this will help Danielle at all, but I have the red LightStim (which includes near IR) and although I have seen some skin improvement, I don’t know how much, or if any, of that can be attributed to LS. I went with red because I also wanted to use it on bruises and sore muscles, and it seems to do very little to nothing for even small bruises with a 30 minute treatment time. Anyone considering the LS devices should take the time to look at all the options before springing for one. I went with LS because they’ve been around for years and are a well-known company in the US, but I’m here because I’m now convinced that the LS simply is not powerful enough to deliver results. (They make a point of not disclosing the power output on their devices, but the lackluster results on bruises from the device they specifically sell for healing doesn’t instill confidence)

      Really appreciate this website and all the info here. Thanks for making this info and the devices available, Joe.

  35. kris says:

    I have scar tissue between first and second metatarsals from a lisfranc injury in a fall three months ago. They didn’t catch it in the initial x rays. I am opting to wait and watch instead of surgery, and wondering if red light would be a possibility for eliminating the scar tissue? If so, which device and how long?

    • Joe says:

      I don’t think light therapy will ‘eliminate the scar tissue’, but it will help to some extent at improving. Light therapy is more useful as a means to prevent scar tissue at the time of injury, rather than actually eliminate well established scars years after the injury.
      Something that penetrates well like this is most suitable:

  36. kim says:

    Advice for choosing a light for two very different purposes?? I’d like light therapy for facial skin wrinkles, and also a light for deep muscle healing. I am concerned that your combo light will penetrate too deeply for facial skin, and not have enough LEDs to truly help deep muscle pain. Is this correct? Would I need two different lights?

    • Joe says:

      The amount of LEDs is irrelevant because there are different classes/power of LEDs.
      The factor that matters is the power density / irradiance (mW/cm2). You need higher than 100mW/cm2 for deeper penetration in general. You want less than 100, but more than 20mW/cm2 for skin treatment.
      So what that means is you need to adjust the distance you use something like our Combo light depending on if you want deeper penetration or not.
      So you would use it closer than 20cm for deeper penetration. Between 20cm and 50cm for skin treatment.

  37. Jenn says:

    What are your thoughts on the Abrastim 200 device? For a $35,000 device I would like to understand if it is superior in any way given it’s high price tag

    • Joe says:

      I have never heard of it before, but it doesn’t look like a light therapy device. From what I can see, it seems to be a facial massage device, with an optional LED attachment of 0.005 watts power.
      I don’t like to criticise other vendor’s products without knowing the full treatment, however I will say that in general, any device with such a low power will have absolutely no effects in terms of photobiomodulation.

  38. Francie says:

    Hi – my daughter had surgery on her nose and upper lip. We were thinking that either the red and/or infrared light therapy might help stimulate healing. Can one of your lights be used for that purpose, and if so which one? And also what dosage (time per treatment etc, how far away from the skin etc) should be used.

    • Joe says:

      Sure, pretty much all of them are suitable for surgery like that. Red lights will be better for more superficial skin damage from surgery. Near infrared will be better for more substantial deeper tissue damage from surgery. In your case, maybe a combo light would be the most ideal. Using the light at around 50-100mW/cm2 is probably ideal for fairly deeper surgical damage. 5-10 minutes is fine from about 10-20cm away.

  39. Pooja says:

    I read the reference you provided for dosage details for back pain and muscle pain. It says the total energy irradiated on muscle should be 83.4 J. But the dosage column here says 80 J/cm2 is right. So what should I consider – The total energy irradiated(J) per muscle or energy density(J/cm2) per muscle?
    Could you please explain?
    Thank you!

    • Joe says:

      The correct dose units are power density – J/cm2. Total energy is not useful.
      Those referenced studies are just to get an idea. For muscles I think you need quite a large dose (70J/cm2+), from a light source of 100mW/cm2 or higher.

  40. Lisa Query says:

    Joe, can you please direct me to a specific brand/brands at reasonable cost of a solar meter to check power denisity on various led/red light therapy devices? Amazon seems to have several products entitled “solar meter” for over 200 bucks. That seems overkill for checking a couple of lights. Help? Thanks!

    • Joe says:

      Due to the materials involved in this kind of sensor, that’s the normal price, unless you can find one second hand on ebay or somewhere. Perhaps you can buy one that can be returned for a refund.

  41. Kat says:

    Hey Joe! Two quick questions:
    1) When is the combo device going to be in stock?
    2) Does NIR not work for wrinkles and collagen production? I hear it kind of just bypasses the surface/superficial layers of skin and mostly benefits the deeper tissues, muscles, organs and bones. BUT, your infrared light says it does say the spectrum includes SOME visible red (680 nm), so what percentage would you say is 680 nm and is it enough for me to see some surface skin results (light wrinkles and collagen boost)?


  42. Keith Reynolds says:

    I have aBulb: ABI 25W Deep Red 660nm LED Light Bulb. I have through these posts here and am confused a bit. I would like to know the time and distance to use this for tissue repair, arthritis, genital assistance, and hair regrowth. How long should I use the light and from what distance? I would appreciate the answer in US terms. Thank you.

    • Joe says:

      To use a light for therapy, you need to measure the power density as described in this article. Without the power density readings, there is no way to advise on how close or how far to use your light.
      In addition to measuring the light intensity, you should also measure the EMFs.

  43. Jody Rein says:

    I have severe arthritis in my knees with no cartilage between patella and femoral groove. Planning on partial patella femoral knee replacement in a few weeks. I would also like a product that will work on my facial wrinkles and my husband’s hair loss. What product would you recommend and how to use it? Will the near ir rays heat up a metal prosthetic device? Will it help healing with the prosthetic device?

  44. Gloria Butner says:

    Pretty technical. So if I want to improve my facial collagen how strong of a bulb do I need?

  45. Jay says:

    What is your recommendation on type of light (wavelength, frequency) and dosage for neuropathic facial pain (trigeminal nerve)? Thank you!

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