Photobiomodulation (PBM) red light therapy has gained attention as a potential method to support testosterone production in men, but does the evidence support its use? PBM uses specific wavelengths of red and near-infrared light to stimulate cellular function, theoretically enhancing mitochondrial activity in testosterone-producing Leydig cells. Whilst animal studies and small-scale human trials suggest modest hormonal effects, robust clinical evidence remains limited. This article examines the current scientific understanding of PBM for testosterone support, safety considerations, and evidence-based alternatives. Men experiencing symptoms of low testosterone should consult their GP for proper assessment before considering experimental therapies.

What Is PBM Red Light Therapy and How Does It Work?

Photobiomodulation (PBM), commonly known as red light therapy, is a non-invasive treatment that uses specific wavelengths of light—typically in the red (630–700 nm) and near-infrared (700–1100 nm) spectrum—to stimulate cellular function. Unlike ultraviolet (UV) light, these wavelengths are generally considered low risk when used correctly and according to manufacturer guidance.

The proposed mechanism centres on the activation of cytochrome c oxidase, an enzyme in the mitochondrial respiratory chain. When red or near-infrared light is absorbed, it may enhance adenosine triphosphate (ATP) production, the primary energy currency of cells. This increased cellular energy could potentially improve tissue repair, reduce inflammation, and modulate oxidative stress. PBM has been investigated for various applications, including wound healing and pain management, though it's worth noting that NICE does not recommend phototherapy for certain conditions such as low back pain.

In recent years, interest has grown around PBM's potential effects on endocrine function, particularly testosterone production in men. The testes contain Leydig cells responsible for synthesising testosterone in response to luteinising hormone (LH) from the pituitary gland. Proponents suggest that by enhancing mitochondrial function in these cells, red light therapy might support optimal testosterone synthesis. However, it is important to note that this application remains experimental, and robust clinical evidence is still emerging. Understanding the biological plausibility is essential before considering PBM as a therapeutic option for hormonal health.

Can Red Light Therapy Increase Testosterone Levels in Men?

The question of whether red light therapy can meaningfully increase testosterone levels in men is complex and not yet definitively answered by high-quality clinical trials. The hypothesis is based on animal studies and preliminary human data suggesting that targeted light exposure to the testes may enhance Leydig cell function and, consequently, testosterone production. Some small-scale studies have reported modest increases in serum testosterone following scrotal or testicular exposure to red or near-infrared light, but these findings require cautious interpretation.

Key considerations include:

• Limited human evidence: Most research has been conducted in rodents or involved very small sample sizes without rigorous controls. Large, randomised controlled trials (RCTs) in men are lacking.

• Variability in protocols: Studies differ widely in wavelength, power density, duration, and anatomical site of application, making it difficult to draw firm conclusions.

• Baseline testosterone levels: Men with clinically low testosterone (hypogonadism) may respond differently to interventions compared to those with normal levels. There is a lack of high-quality evidence for clinically meaningful increases in testosterone with PBM therapy.

• Regulatory status: No devices are UKCA or CE-marked specifically for increasing testosterone; use for this purpose would be outside the device's intended purpose.

• Fertility considerations: Increased scrotal temperature can reduce sperm quality, so caution is advised if trying to conceive.

While the biological rationale is plausible, current evidence does not support red light therapy as a first-line or proven treatment for low testosterone. Men experiencing symptoms of hypogonadism should seek assessment from their GP, who may arrange two early-morning (7–11 am) total testosterone tests on separate days, along with LH/FSH, prolactin and possibly SHBG/free testosterone measurements. Levels below 8 nmol/L are generally consistent with hypogonadism, while 8–12 nmol/L is considered borderline.

Scientific Evidence for PBM and Male Hormone Health

The scientific literature on PBM and testosterone is nascent and largely exploratory. A handful of animal studies have demonstrated that low-level light therapy applied to the testes can increase testosterone levels, potentially through enhanced mitochondrial activity and reduced oxidative stress in Leydig cells. For example, research in rats has shown that near-infrared light exposure may improve testicular function and sperm quality, alongside modest hormonal changes.

In humans, the evidence base is considerably weaker. A small pilot study published in a peer-reviewed journal reported that men exposed to bright white light (approximately 10,000 lux, simulating sunlight) experienced increases in testosterone and sexual satisfaction. However, this study did not test red or near-infrared PBM specifically, and the methodology has been critiqued for lack of blinding and control. Another preliminary investigation involving scrotal exposure to red light suggested a transient rise in testosterone, but the study was not placebo-controlled, and the clinical significance of the observed changes remains uncertain.

Current limitations include:

• Absence of RCTs: No large-scale, double-blind, placebo-controlled trials have been conducted to date.

• Heterogeneous populations: Studies have not consistently defined baseline testosterone status or excluded confounding factors such as diet, exercise, or concurrent medications.

• Short follow-up periods: Long-term safety and efficacy data are not available.

Until more robust evidence emerges, healthcare professionals should counsel patients that PBM for testosterone enhancement is investigational. NICE Clinical Knowledge Summaries on testosterone deficiency do not currently include red light therapy as a recommended intervention. Men considering this approach should discuss it openly with their clinician and prioritise evidence-based treatments where appropriate.

How to Use Red Light Therapy Safely for Testosterone Support

For men interested in exploring red light therapy, safety and informed decision-making are paramount. While PBM is generally considered low-risk when used appropriately, there are important considerations to ensure safe and responsible use, particularly when targeting sensitive anatomical areas such as the testes.

Practical safety guidance:

• Consult a healthcare professional first: Before starting any new therapy for hormonal concerns, speak with your GP. Symptoms attributed to low testosterone may have other underlying causes requiring investigation, such as thyroid disorders, diabetes, or medication side effects.

• Choose reputable devices: If proceeding, select devices that comply with UK and EU safety standards (UKCA or CE marking where applicable). Avoid unregulated or poorly documented products.

• Follow manufacturer instructions: Adhere strictly to the manufacturer's recommended irradiance, distance, and exposure limits. Overexposure does not equate to better results and may cause tissue heating or discomfort.

• Protect sensitive tissues: When applying light near the genital area, ensure appropriate distance to avoid thermal injury. Use appropriate eye protection and never direct light at the eyes.

• Monitor for adverse effects: Discontinue use and seek medical advice if you experience pain, swelling, skin changes, or any unexpected symptoms. Report suspected adverse incidents with medical devices to the MHRA via the Yellow Card Scheme.

• Important cautions: Avoid use if trying to conceive, as scrotal heating may impair spermatogenesis. Do not use over areas of known or suspected cancer. Seek urgent GP review for new testicular pain, swelling, or lumps.

• Avoid reliance on unproven therapies: Do not delay or substitute evidence-based treatments (e.g., testosterone replacement therapy prescribed by a specialist) with experimental approaches.

It is also important to recognise that PBM should not be viewed as a standalone solution. Lifestyle factors—including sleep, nutrition, physical activity, and stress management—play critical roles in hormonal health and should be optimised alongside any adjunctive therapies.

Other Evidence-Based Ways to Improve Testosterone Naturally

For men seeking to support healthy testosterone levels, several lifestyle and behavioural interventions have stronger evidence than red light therapy. These approaches are recommended by authoritative bodies as foundational strategies for optimising male hormonal health.

Weight management and body composition: Obesity, particularly visceral adiposity, is strongly associated with lower testosterone levels. Adipose tissue converts testosterone to oestrogen via the enzyme aromatase, creating a negative feedback loop. Achieving and maintaining a healthy body weight through balanced nutrition and regular physical activity can improve testosterone levels in overweight or obese men.

Resistance and high-intensity exercise: Structured exercise, especially resistance training and high-intensity interval training (HIIT), has been shown to acutely elevate testosterone, though sustained baseline increases are small and inconsistent. Follow the UK Chief Medical Officers' guidelines of at least 150 minutes of moderate-intensity or 75 minutes of vigorous-intensity aerobic activity per week, combined with muscle-strengthening activities on two or more days.

Adequate sleep: Sleep deprivation and poor sleep quality are linked to reduced testosterone production. Most testosterone is released during sleep, particularly during REM cycles. Aim for 7–9 hours of quality sleep per night, and address any underlying sleep disorders such as obstructive sleep apnoea.

Stress reduction: Chronic psychological stress elevates cortisol, which can suppress the hypothalamic-pituitary-gonadal axis and reduce testosterone synthesis. Mindfulness, cognitive behavioural therapy (CBT), and relaxation techniques may help mitigate stress-related hormonal disruption.

Nutritional optimisation: Consider testing for and correcting deficiencies in key micronutrients involved in testosterone synthesis, such as vitamin D, zinc, and magnesium, rather than routine supplementation. Avoid exceeding UK recommended intakes. A balanced diet rich in whole foods, healthy fats, and lean protein supports overall endocrine function.

Limit alcohol and avoid anabolic steroids: Excessive alcohol consumption and illicit use of anabolic steroids can suppress natural testosterone production and cause long-term harm.

If symptoms of low testosterone persist despite lifestyle modification, or if testosterone levels are clinically low on blood testing, referral to an endocrinologist for further assessment and consideration of testosterone replacement therapy (TRT) may be appropriate. TRT is a well-established treatment for confirmed hypogonadism but has contraindications including desire for fertility and prostate or breast cancer. It requires specialist monitoring of haematocrit, PSA, and liver function.

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