A handful of supplements have shown real effects on testosterone levels in clinical trials, but the results depend heavily on your starting point. Men who are deficient in key nutrients like vitamin D or zinc see the most dramatic improvements. For men with already-normal levels, most supplements produce modest effects or none at all. Here’s what the evidence actually supports.
Vitamin D: The Strongest Case
Vitamin D is the supplement with the most straightforward evidence behind it, particularly if your levels are low. In a year-long trial of men whose vitamin D blood levels were in the deficient range, taking about 3,300 IU daily raised total testosterone from 10.7 to 13.4 nmol/L, a roughly 25% increase. Free testosterone and bioactive testosterone both rose significantly as well. The placebo group saw no change.
The key detail: these men started with low vitamin D and testosterone at the bottom end of the normal range. If your vitamin D is already adequate, supplementing more is unlikely to push testosterone higher. A simple blood test can tell you where you stand. Deficiency is common, especially in people who spend most of their time indoors, live at higher latitudes, or have darker skin.
Ashwagandha: Modest but Consistent
Ashwagandha is one of the more studied herbal options. In a placebo-controlled crossover trial of overweight men aged 40 to 70, eight weeks of supplementation produced a 14.7% greater increase in testosterone compared to placebo. The same study found an 18% greater increase in DHEA-S, a precursor hormone the body converts into testosterone and other sex hormones.
The proposed mechanism involves stress reduction. Ashwagandha is classified as an adaptogen, meaning it helps regulate the body’s stress response. Chronically elevated stress hormones compete with testosterone production for the same raw materials. By lowering that stress burden, ashwagandha may give the body more room to produce testosterone. This makes it a better fit for men dealing with high stress, poor sleep, or general fatigue rather than someone who’s already well-rested and relaxed.
Fenugreek: Large Numbers, Small Studies
Fenugreek seed extract has produced some of the most eye-catching numbers in testosterone research. In an eight-week trial of men doing resistance training, the group taking a fenugreek glycoside extract saw free testosterone rise by 98.7% from baseline, compared to 48.8% in the placebo group. That’s a meaningful gap, though it’s worth noting the placebo group also saw large increases, likely from the exercise itself.
Fenugreek appears to work by blocking two enzymes that convert testosterone into other hormones: one that turns it into estrogen and another that converts it into a more potent form called DHT. By slowing these conversions, more free testosterone stays circulating in the blood. The catch is that most fenugreek studies are small pilot trials, so these percentages should be interpreted cautiously until larger studies confirm them.
Boron: Small Dose, Quick Response
Boron is a trace mineral that doesn’t get much attention, but a small study found notable results in just one week. Men taking 6 mg of boron daily saw free testosterone rise from an average of 11.83 pg/mL to 15.18 pg/mL, roughly a 28% increase. The study was small (eight participants), so the finding needs replication, but the speed and size of the response are noteworthy. Boron is inexpensive and widely available, and 6 mg daily is a low dose with minimal risk.
Zinc and Magnesium (ZMA): Only If You’re Deficient
ZMA, a combination of zinc, magnesium, and vitamin B6, is one of the most popular testosterone supplements in the fitness world. The evidence, however, is underwhelming for healthy men. A controlled trial in experienced resistance-trained males found no significant differences between ZMA and placebo in total testosterone, free testosterone, growth hormone, or cortisol. Zinc levels increased modestly but not enough to reach statistical significance.
That doesn’t mean zinc and magnesium are irrelevant. Both minerals are essential for testosterone production, and deficiency in either one will suppress your levels. Athletes who sweat heavily, people who eat very restricted diets, and older adults are the most likely to be low. If you fall into one of those categories, correcting a deficiency with supplementation can restore testosterone to normal. But stacking extra zinc and magnesium on top of adequate levels won’t push testosterone above your baseline.
D-Aspartic Acid: Short-Lived Effects
D-aspartic acid (DAA) is an amino acid that stimulates signaling between the brain and the testes. An early study found that 12 days of supplementation at about 3 grams daily increased testosterone by 42% and luteinizing hormone (the signal that tells the testes to produce testosterone) by 33%. Three days after stopping, levels remained elevated, suggesting the compound lingered in testicular tissue and kept stimulating production.
The problem is that longer studies haven’t replicated these results. A 28-day trial found no effect on total testosterone, free testosterone, or any related hormone. Another study combining DAA with other ingredients found no significant testosterone increase after 14 or 28 days. The pattern suggests DAA may cause a brief spike that the body quickly adjusts to, making it unreliable for sustained use.
Tongkat Ali: Mixed and Inconsistent
Tongkat Ali (Eurycoma longifolia) is widely marketed as a testosterone booster, but the clinical picture is messy. Results vary dramatically depending on who takes it and for how long. In men diagnosed with age-related androgen deficiency, 200 mg daily for six months significantly increased total testosterone. A study of older physically active adults (ages 57 to 72) found that 400 mg daily for five weeks raised both total and free testosterone. And a four-week study of moderately stressed adults reported a 37% testosterone increase alongside a 16% drop in cortisol.
On the other hand, a four-week trial in exercise-trained men and women at 400 mg daily found no effect on free testosterone, cortisol, or body composition. A 12-week study of sedentary men at 300 mg daily found no changes in testosterone or body composition. Another 12-week trial testing 100 mg and 200 mg daily found no significant differences in free testosterone compared to placebo. The trend in the data suggests Tongkat Ali may help men who are older, stressed, or have declining testosterone, but it doesn’t appear to do much for younger, healthy, or well-trained individuals.
What Actually Matters Most
The single biggest factor determining whether a supplement will raise your testosterone is whether you’re deficient in something. Correcting a vitamin D deficiency, replenishing low zinc, or managing chronic stress through an adaptogen like ashwagandha can produce real, measurable improvements. Stacking supplements on top of already-normal levels rarely moves the needle in a meaningful way.
Sleep, body composition, and exercise have a larger impact on testosterone than any supplement. Resistance training alone can raise free testosterone significantly, as the placebo groups in several of the studies above demonstrated. Losing excess body fat reduces the conversion of testosterone to estrogen. Getting seven to nine hours of sleep protects overnight testosterone production, which peaks during deep sleep cycles. Supplements work best as a complement to those fundamentals, not a replacement for them.