Red Light Therapy from a Flashlight? Is it possible?

Red Light Therapy from a Flashlight? Is it possible?

Can we use a red tactical flashlight for red light therapy? Can something so simple and affordable really be a clever biohack for photobiomodulation? Lets test it!

We commonly see many popular brands selling what looks like fancy flashlights as red light therapy. Some even get FDA clearance or approval with some pretty impressive claims and specifications.

We can also search for "red tactical flashlights" and "infrared tactical flashlights" and find these same wavelengths of 660nm or 850nm in a much more affordable format. These are commonly used for hunting, surveillance, or military.

So this begs the question, can we use a tactical flashlight as a red light therapy tool? I wanted to find out.

So I ordered two tactical flashlights directly from the manufacturers, and specifically requested a custom flashlight with a 660nm LED.

I contacted:

Wealth Electrical

Topcom Flashlight

Both of them produced for me essentially identical-looking flashlights. So lets go over some of my testing and observations.

red flashlights for photobiomodulation red light therapy


One of the flashlights emits a deep red (from Wealth). The other one was more orange-red (from Topcom). 

red light therapy flashlights color

This tells us something important about the industry:

1. LEDs are not always the same. Even if they are both 660nm LEDs, if one has a tightly centered spectrum it will appear deeper red. If the other has a wider spectrum, it will have more orange or yellow component to it.

2. Topcom might have simply given me a 635nm LED, since those are more common and cheaper. They might have thought it was OK to substitute the wavelength, or did it out of ignorance.

3. This is why it is always important to verify your wavelengths, or purchase from a company that verifies the wavelengths.

Perhaps I will update this blog if I ever get a hold of a spectrometer for myself. I'm not going to send these to the lab. Overall whether it is actually 660nm or 635nm, both wavelengths are fine for photobiomodulation. So I'm not too worried, and it is nice to have different wavelength options for me to use.


I measured intensity with a Tenmars Solar Power Meter and my SANWA laser meter. As we found in my blog about Solar Power meters, the Tenmars will read falsely high, and might be why many of these flashlight peddlers claim such ridiculously high intensities.

Tenmars Solar Power Meter:

Wealth Flashlight (deep red) - 190 mW/cm^2

Topcom Flashlight (orange/red) - 76 mW/cm^2

red light therapy flashlight intensity tenmars solar power meter

We see the Tenmars meter is giving us impressive numbers, particularly on the Deep-Red flashlight. This is an unrealistic number, as getting flashed in the eye with 190mW/cm^2 would be dangerous. As an engineer I have learned it is good to first apply common sense when you are interpreting a measurement, and this one hardly seems real.

SANWA laser power meter:

Wealth Flashlight (deep red) - 37mW / 0.636cm^2 * .925 = 53.8 mW/cm^2

Topcom Flashlight (orange/red) - 30mW / 0.636cm^2 * 1 = 47.1 mW/cm^2

red light therapy intensity measurement gembared flashlight

With the SANWA we get the reading in mW, so we have to divide by the sensor area of 0.636cm^2 to get the mW/cm^2. Then we multiply by the correction factor, for deep red I chose 0.925, for orange/red I chose 1.0.

With measurements at around 50mW/cm^2, this is a really ideal amount of intensity that is effective but also safe to use. And at least the SANWA laser meter is giving us logical measurements compared to the Tenmars Solar power meter.


Yes, these flashlights both have "pulsing" modes! In the dim mode, they actually are using Pulsed Width Modulation (PWM), which as implied by the name is a form of pulsing to reduce the perceived brightness.

For the measurements, I am using a DIY flicker meter that I built based on an oscilloscope and photo-diode. Blog post coming soon on how to build your own!

Both have practically the same pulsing modes:

Visible Flashing mode: about 8Hz

8hz pulsed red light therapy flashlight

Dim Mode:  253Hz (PWM)

 flicker meter pulsed frequency measurement red light therapy

So the interesting thing about PWM and pulsing is that even though might look like it is dimmer, but it is actually the same peak intensity. Since the duty cycle for both modes is about 50%, then proper dosage strategy would tell us that the average intensity is half of the intensity numbers that I show above, when used in a pulsed mode.

8Hz is a particularly interesting pulse rate for me, since the significance of being close to the Schumann resonance of 7.83Hz, as well as being close to the very popular pulsing frequency of 10Hz.

I can't think of anything interesting about 253Hz pulsing, but it is a good option to try out.

So these flashlight modes could be a very cheap way to try out some pulsing techniques!


Because it is so easy to press these flashlights into the skin, we can really optimize the penetration. See our blog post about optimizing penetration.

I can easily see the light penetrating through my knuckle when I press each one into my hand. Showing that I can get all of the light into my skin, rather than using a panel at a distance allowing much of the light to reflect off of the skin.

red light therapy penetration through hand


Both are compatible with either a 18650 lithium battery, or 3 AAA batteries. Both seem to output the same intensity regardless of battery type. Obviously the lithium is nice because it is rechargeable, but I find it causes the flashlight heats up dramatically. It might be because of the cheap lithium battery that I used is overheating, or the thin-walled metal of this cheap flashlight simply doesn't manage the heat well.

batteries red light therapy portable lithium


Overall these flashlights offer a cheap and simple way to get effective intensity for red light therapy. You can even dabble in a very affordable version of pulsing frequencies, if the flashlights include multiple modes!

Unfortunate the wavelengths might be variable depending on the source, but as long as we trust our eyes and it emits red, then that is close enough for a cheap flashlight.

I decided against both of these models in my GembaRed store, since it is easy to find red tactical flashlights on Amazon or eBay. Also I was concerned about them overheating in people's hand

So, we will keep searching for affordable and interesting biohacks with red lights!