NAC (N-acetylcysteine) does not reliably increase testosterone in most people. When researchers pooled data from randomized controlled trials in men, NAC supplementation showed no significant difference in testosterone levels compared to placebo. The picture is more nuanced than a simple yes or no, though, because NAC’s effect on testosterone depends heavily on who’s taking it and why.
What the Clinical Evidence Actually Shows in Men
The best evidence comes from a meta-analysis published in the American Journal of Men’s Health, which combined data from two randomized controlled trials involving 311 men with unexplained infertility. The pooled results found no significant difference between NAC and placebo in raising testosterone levels. The same held true for other reproductive hormones like luteinizing hormone, follicle-stimulating hormone, and prolactin.
That said, one individual trial within this body of research did find a modest bump. In a study of 468 infertile men published in The Journal of Urology, the NAC group saw average testosterone rise from about 18.1 to 20.1 nmol/L after 26 weeks of supplementation, a statistically significant increase. But here’s the catch: by week 56, testosterone had returned to baseline. The effect was temporary, and when combined with other trial data, it wasn’t strong enough to reach statistical significance overall.
So while individual studies have shown small, short-lived increases, the weight of current evidence says NAC is not a reliable testosterone booster in men. What it does appear to improve is sperm quality. The same meta-analysis found NAC significantly improved sperm concentration, motility, volume, and normal shape in infertile men, all without meaningfully changing hormone levels.
How NAC Affects Testosterone in Women With PCOS
In women with polycystic ovary syndrome (PCOS), NAC has the opposite effect. A systematic review and meta-analysis found that NAC supplementation significantly reduced total testosterone levels in women with PCOS. This makes sense in context: PCOS is characterized by excess androgens, and lowering testosterone is a therapeutic goal, not a side effect. NAC also increased follicle-stimulating hormone (FSH) in these women, which supports healthier ovulation cycles.
This highlights an important point about NAC. It doesn’t simply push testosterone in one direction. Instead, it appears to nudge hormonal balance back toward a healthier range depending on what’s off in the first place.
Why NAC Protects Testosterone Under Stress
Where NAC does show a clear testosterone-related benefit is in protecting the testes from oxidative damage. NAC is a precursor to glutathione, the body’s most abundant internal antioxidant. When testicular tissue is exposed to environmental toxins or oxidative stress, testosterone production drops because the cells responsible for making it (Leydig cells) get damaged.
In animal studies, exposing mice to an industrial pollutant caused significant decreases in testosterone and visible damage to the seminiferous tubules, the structures where sperm develop. Adding NAC to the treatment reversed those changes, restoring both testosterone levels and testicular tissue structure. NAC achieved this by replenishing glutathione levels inside cells and reducing the kind of fat-based oxidative damage that kills sperm-producing and hormone-producing cells.
This is an important distinction. NAC doesn’t appear to boost testosterone above your normal baseline. But if something is actively suppressing your testosterone through oxidative damage, whether that’s environmental toxins, chronic inflammation, or other stressors, NAC may help prevent that suppression. Think of it less as a gas pedal and more as removing the brakes.
Typical Dosages Used in Studies
Most clinical trials have used 600 mg taken three times daily, totaling 1,500 mg per day. Study durations ranged from 6 to 26 weeks, with the hormonal changes observed in individual trials appearing around the 26-week mark. The studies showing sperm quality improvements used similar dosages and timeframes.
NAC has a well-established safety profile at these doses. The most common side effect is gastrointestinal discomfort, particularly nausea and vomiting, which occurs in up to 23% of people taking it orally. The sulfur content gives NAC a smell reminiscent of rotten eggs, which contributes to the nausea. Skin itching and redness have also been reported, though less frequently. Serious reactions are uncommon at standard supplemental doses.
The Bottom Line for Testosterone
If you’re a generally healthy man hoping NAC will meaningfully raise your testosterone, the current evidence doesn’t support that expectation. Meta-analyses consistently show no significant hormonal changes compared to placebo. If you’re dealing with male infertility, NAC may still be worth considering for its benefits to sperm quality, even though it likely won’t shift your testosterone numbers. And if you’re a woman with PCOS, NAC actually works in the opposite direction, helping bring elevated testosterone down toward a healthier range.
NAC’s real strength is as an antioxidant that protects reproductive tissue from damage. In situations where oxidative stress is actively harming testosterone production, it can help preserve normal levels. But “preserving normal” is different from “boosting higher,” and that distinction matters when deciding whether this supplement fits your goals.