Melatonin is not bad for most males at standard doses. The concern that it lowers testosterone or harms male reproductive health comes up often, but the clinical evidence doesn’t support it. A study of over 7,600 U.S. adult men found no association between melatonin use and low testosterone levels, with typical doses around 1 to 3 mg per day. That said, melatonin does interact with the hormonal system in ways worth understanding, especially at higher doses or with long-term use.
Effect on Testosterone Levels
The most common worry men have about melatonin is that it tanks their testosterone. A large analysis using national health survey data looked at men with a median age of 47 and median testosterone of about 390 ng/dL. Among melatonin users taking low doses (median of 1 mg/day), there was no statistically significant link to low testosterone. The odds ratio was essentially 1.0, meaning melatonin users were no more likely to have low testosterone than non-users.
Melatonin does interact with the hormonal chain that controls testosterone production. It binds to receptors in the brain that can influence the release of gonadotropin-releasing hormone, which is the starting signal for testosterone production. In animal studies and in research on girls with precocious puberty, melatonin has been shown to dial down this signaling pathway, reducing levels of luteinizing hormone and follicle-stimulating hormone. But this suppressive effect has been demonstrated primarily in specific clinical contexts, not in healthy adult men taking normal supplement doses. The human evidence in adult males simply hasn’t shown a meaningful testosterone drop.
Sperm Quality and Fertility
If anything, melatonin appears to help male fertility rather than hurt it. A systematic review of the research concluded that sperm quality parameters generally improve with melatonin supplementation. Melatonin is a potent antioxidant, and sperm cells are particularly vulnerable to oxidative damage. By neutralizing reactive oxygen species, melatonin helps protect sperm DNA integrity and stabilize the energy-producing structures inside sperm cells.
In lab studies using human sperm, melatonin exposure improved motility (the ability of sperm to swim effectively) and reduced the number of immobile sperm. It also decreased markers of cell death and DNA fragmentation in both normal and low-count sperm samples. One study found that melatonin increased the proportion of sperm with adequate surface markers for fertilization in both healthy and subfertile samples. These are lab findings rather than large clinical trials, but the direction of the evidence is consistently positive for sperm health.
Sexual Function and Desire
A randomized clinical trial comparing melatonin, a prescription sleep drug, and placebo over 30 days found that the melatonin group experienced a significant increase in sexual desire scores. Overall sexual function scores also improved modestly in the melatonin group (from 38 to 41), while the placebo and sleep drug groups saw slight declines. Erectile function scores didn’t change significantly in any group, suggesting melatonin neither helps nor hurts erections at standard doses.
This was a specific population (men in opioid addiction treatment), so the results may not generalize perfectly to all men. But the takeaway is that melatonin didn’t impair sexual function in any measured domain and may have given libido a small boost, possibly through its effects on sleep quality and stress reduction.
Puberty Concerns in Boys
Parents sometimes worry that giving melatonin to boys could delay puberty, since melatonin naturally drops as puberty begins. A two-year study followed 80 children and adolescents (ages 2 to 17.5) taking prolonged-release melatonin at doses of 2 mg, 5 mg, or 10 mg nightly. Physicians tracked pubertal development using standard staging assessments throughout the study. Changes in weight, height, BMI, and pubertal status all stayed within normal ranges for age, with no evidence of delayed development. There were also no withdrawal effects when the children stopped taking it.
This is reassuring, though it’s worth noting that two years is a limited window for tracking something as gradual as puberty. For boys taking melatonin over many years, the long-term data is thinner.
Gynecomastia and Prolactin
There is a small signal linking melatonin to breast tissue changes in men, but it’s limited to case reports and pharmacological-dose studies. One case report described a man with ALS who developed painful breast tissue enlargement after prolonged use of high-dose melatonin. Separately, a study found that a single large dose of melatonin caused an isolated spike in prolactin (the hormone that can stimulate breast tissue growth) without affecting testosterone or other reproductive hormones.
This doesn’t mean standard doses cause breast enlargement. Prolactin elevation from a single large dose is a different thing from the sustained high prolactin that leads to gynecomastia. But if you’re taking melatonin at doses well above the typical 1 to 5 mg range and notice breast tenderness, it’s worth paying attention to.
Practical Dosing for Men
For short-term insomnia, a 2 mg slow-release tablet taken one to two hours before bed is a standard starting point. For jet lag, 3 mg taken at bedtime for up to five days is typical. For longer-term sleep issues, doses can go up to 10 mg under medical guidance, though most sleep specialists recommend starting as low as possible since melatonin’s effectiveness doesn’t scale linearly with dose.
Most of the hormonal concerns that circulate online are based on animal research, studies in women or children with specific conditions, or theoretical mechanisms that haven’t played out in human male data. At doses under 5 mg, the evidence consistently shows that melatonin is well tolerated in men without meaningful effects on testosterone, fertility, or sexual function. The main practical side effects are the ones that affect everyone: next-day grogginess, vivid dreams, and occasionally headaches.