Red light therapy panels have gone from physical-therapy clinics to bedroom corners in a few years, and the marketing claims have expanded right along with the install base — skin, recovery, sleep, and, increasingly, testosterone. The pitch is straightforward: shine red or near-infrared light on the testes, and the Leydig cells that produce testosterone respond by making more of it. Search interest in the question has grown fast enough that it's worth answering carefully, because the honest answer is more nuanced than either the marketing or the skeptics usually present it: there's real biology behind the idea, real data in animals, and a near-total absence of the human evidence that would actually justify a claim about testosterone in men.
Photobiomodulation (PBM) — commonly called red light therapy — has raised serum testosterone in rats and mice when light was applied directly to the testes, and one study found a 54% testosterone increase in male donkeys under red light exposure. The proposed mechanism (improved mitochondrial ATP production in Leydig cells) is well-documented in cell and animal research. But controlled human trials measuring testosterone before and after red light exposure in men are not available in the published literature; the closest human data covers sperm motility and testicular pain, not testosterone levels. Until that evidence exists, red light therapy should be treated as an unproven, experimental approach — not a substitute for testing your actual levels.
What red light therapy actually is
Red light therapy is a form of photobiomodulation (PBM) — the use of specific wavelengths of visible red (roughly 600–700nm) or near-infrared (roughly 700–1100nm) light to influence cell activity, typically delivered by LED panels or low-level lasers. The mechanism researchers propose starts inside the cell: red and near-infrared light is absorbed by cytochrome c oxidase, an enzyme in the mitochondrial electron transport chain, which can increase ATP (cellular energy) production and reduce oxidative stress in the exposed tissue.
That mechanism is genuinely established in photobiomodulation research generally, which is why PBM is being studied across dermatology, wound healing, and musculoskeletal recovery. The open question isn't whether red light does anything at the cellular level — it's whether that cellular effect, applied to the testes, translates into a clinically meaningful hormone change in a living man. That's a much narrower and much less answered question, and it's the one this article focuses on.
The animal evidence is real — but it's not human data
Most of what's cited to support "red light raises testosterone" comes from animal studies, and it's worth being specific about what they actually found rather than treating "studies show" as a single undifferentiated claim:
1Rats: a modest, wavelength-specific effect
A study irradiating the testes of Sprague-Dawley rats with either a 670nm or 808nm diode laser for five days found that the 670nm wavelength significantly elevated serum testosterone by day four, while the 808nm wavelength — despite penetrating tissue more deeply — did not produce a significant increase over control.[1] That wavelength-dependence is an important detail: the effect wasn't "more light, more testosterone," it was specific to one wavelength and one protocol.
2Donkeys: a larger effect, still an animal model
A study on male donkeys during their non-breeding season found red LED light exposure raised testosterone by 54% compared to controls (5.40 vs. 3.50 ng/mL), alongside changes in other reproductive hormones.[2] This is a frequently cited figure in consumer marketing, but it comes from a seasonally-breeding animal with a fundamentally different reproductive endocrinology than humans, not a human trial.
3Stroke-model rats: no effect at all
A separate study using PBM in a rat model of post-stroke cerebrovascular recovery specifically looked for testosterone changes and found none — the authors noted this contrasted with earlier reports of PBM raising testosterone when applied directly to the testes in rats and mice, suggesting the effect (where it exists) may depend heavily on the tissue targeted and the specific protocol used.[3]
Put together, the animal literature shows a plausible, mechanism-consistent effect that shows up in some protocols and species and not others — not a settled, reproducible finding even within animal research, let alone one that has been shown to carry over to humans.
What human studies actually show
This is the part most red-light-and-testosterone content skips past quickly, and it's the most important part: there is no published, controlled human trial that measured testosterone levels in men before and after a course of red light therapy and found a significant increase. The human PBM research that does exist targets adjacent but different outcomes:
- Sperm motility, not testosterone. Multiple in-vitro human studies have shown that red and near-infrared laser exposure can increase sperm motility and mitochondrial energy metabolism in semen samples from men with asthenozoospermia (reduced sperm motility) — a 2024 study found 1W of 810nm PBM significantly improved progressive motility compared to control.[4] This is a real, replicated finding — but it measures sperm function in a lab dish, not circulating testosterone in a living man.
- Testicular pain and sexual satisfaction, not testosterone levels. A randomized, double-blind, placebo-controlled trial in men with chronic testicular pain found that low-level laser therapy (both red and infrared) significantly reduced pain and improved self-reported sexual satisfaction scores at 6 and 12 weeks compared to placebo.[5] That's a legitimate positive human RCT result — but it didn't report testosterone measurements, so it can't be used as evidence for a hormone effect, even though it's sometimes cited that way.
- Full-body PBM in athletes: no testosterone effect found. A study on full-body photobiomodulation in male water polo athletes, looking at recovery and inflammation markers across repeated competition days, found no effect on testosterone.[6] This is the closest thing to a human study that directly measured testosterone as an outcome, and it was negative.
The pattern across the human literature is consistent: real effects on sperm motility and testicular pain, a biologically plausible mechanism, and an absence of positive human testosterone data. That gap between mechanism and outcome is exactly why a claim like "red light therapy boosts testosterone" is currently a hypothesis, not a demonstrated effect in men.
Why the theory sounds plausible anyway
It's worth explaining why this claim persists despite the missing human evidence, because the underlying biology isn't nonsense — it's incomplete. Leydig cells, which produce testosterone in the testes, are mitochondria-dense and steroidogenesis (the process of building testosterone from cholesterol) is an energy-intensive, multi-step enzymatic process. If photobiomodulation genuinely increases mitochondrial ATP output in a cell, and that cell's rate-limiting step is partly energy-dependent, a hormonal effect is at least mechanistically conceivable. Some cell-culture research has also found that PBM increased activity of steroid dehydrogenase enzymes involved in testosterone synthesis in cultured porcine granulosa cells, which is a piece of supporting mechanistic evidence, even though granulosa cells are an ovarian, not testicular, cell type.[1]
The honest summary is: the mechanism is plausible enough to justify running a real human trial, and not yet supported by any human trial that's actually been run and published. That's a meaningfully different claim than "the science shows red light therapy raises testosterone," which is the version that circulates in most consumer marketing.
The overlooked risk: heat and sperm production
One point that's frequently left out of red-light-and-testosterone marketing is a direct conflict with a separate, well-established fact about male reproductive physiology: the testes function optimally a few degrees below core body temperature, and sustained scrotal heating is a documented cause of reduced sperm production. Any device delivering meaningful energy directly to the scrotum — laser or LED — carries a real, physiologically grounded risk of local heating, independent of whether it helps or does nothing for testosterone. Devices intended for testosterone-focused scrotal exposure are also not cleared or marketed by regulators for that specific use, since the underlying hormonal claim hasn't been established.
This is a meaningfully different risk-benefit conversation than red light therapy used on skin or joints, where the tissue being irradiated isn't temperature-sensitive in the same way. Anyone considering scrotal red light exposure specifically for a hormonal effect should weigh a real, known risk (heat-related impact on sperm production) against a hormonal benefit that hasn't been demonstrated in humans.
Evidence strength compared
| Study population | Outcome measured | Testosterone result | Evidence quality |
|---|---|---|---|
| Rats (670nm laser, testes) | Serum testosterone | Significant increase, one wavelength only | Animal, small sample, short duration |
| Male donkeys (red LED) | Serum testosterone + reproductive hormones | 54% increase vs. control | Animal, different reproductive endocrinology |
| Stroke-model rats (PBM) | Serum testosterone | No significant change | Animal, different tissue target |
| Men, chronic testicular pain (RCT) | Pain, sexual satisfaction | Not measured | Human RCT, but not a testosterone outcome |
| Male athletes, full-body PBM | Testosterone, inflammation markers | No effect on testosterone | Human study, direct testosterone measure — negative |
What actually moves the result
If low energy, low libido, or other symptoms are what's driving interest in red light therapy, the more useful first step is establishing whether testosterone is actually low in the first place — a question no amount of reading about photobiomodulation mechanisms can answer for you. Our at-home blood test kit checks testosterone and related hormone markers from home with no blood draw and no lab appointment required, so you get an actual number instead of a guess. If a result comes back low, testosterone replacement therapy is the treatment with decades of clinical trial evidence behind it, prescribed only after a licensed clinician reviews your labs and history — not an unproven light-based approach. For a broader look at what symptoms and lab markers are worth tracking as men age, see our guide to testosterone levels by age.
Frequently asked questions
Is there any human study showing red light therapy raises testosterone?
No published, controlled human trial has measured testosterone before and after red light therapy and found a significant increase. The positive testosterone findings come from rodent and donkey studies; the human studies that do exist measured sperm motility, testicular pain, and sexual satisfaction, not testosterone levels — and the one human study that did directly measure testosterone as an outcome found no effect.
Could red light therapy still work, just not proven yet?
That's possible — an unproven effect isn't the same as a disproven one, and the underlying mitochondrial mechanism is biologically plausible. But "not yet disproven" is a different, weaker claim than what's typically implied in marketing, and it's not a basis for skipping an actual lab test if you're concerned about symptoms.
Is scrotal red light therapy safe?
The testes are temperature-sensitive, and sustained localized heating is an established cause of reduced sperm production. Any device delivering meaningful energy to the scrotum carries that physiologically grounded risk, regardless of whether it produces a hormonal benefit. This is a real trade-off to weigh, independent of the unproven testosterone claim.
Does red light therapy help anything related to male reproductive health?
The strongest human evidence relates to sperm motility (in vitro) and testicular pain relief with improved sexual satisfaction (a placebo-controlled human RCT) — both are different outcomes from testosterone production, and neither should be read as evidence of a hormonal effect.
What's the fastest way to know if my testosterone is actually low?
A blood test measuring total and free testosterone, ideally drawn or collected in the morning when levels are highest, is the only reliable way to know. Our at-home lab kit covers this without requiring an in-person blood draw.
Sources
- The effects of low level laser therapy (LLLT) on the testis in elevating serum testosterone level in rats. 2015.
- Effect of Monochromatic Red, Blue, and White Light on Reproductive Hormones of Male Donkeys During the Non-Breeding Season. 2026.
- Photobiomodulation therapy and testosterone changes in a post-stroke rodent model. Cerebrovascular research literature.
- The power of 810nm near-infrared photobiomodulation therapy for human asthenozoospermia. Scientific Reports. 2024.
- Influence of Low-Level Laser Irradiation of the Red and Infrared Spectral Range for Treating Chronic Testicular Pain: A Randomized Clinical Trial. 2024.
- Full-body photobiomodulation therapy effects on inflammation, muscle damage, and hormones in male water polo athletes during repeated match play.
This article is for education and is not a substitute for individualized medical advice. Photobiomodulation research in male reproductive health is preliminary and evolving; no claims here should be read as evidence that red light therapy treats low testosterone. Discuss any symptoms or treatment decisions with a licensed clinician after reviewing lab results.