Testosterone Boosters: What the Evidence Shows, Ingredient by Ingredient

What's actually in the products

A 2020 study in the World Journal of Men's Health took the first 50 "testosterone booster" supplements from a Google search and compared their ingredients with published research. The products contained 109 unique ingredients, an average of 8.3 each. The findings, as reported in the abstract, as shares of products:

• 90% claimed to boost testosterone, 50% claimed to improve libido, and 48% claimed to make men feel stronger.
• Only 24.8% had data showing an increase in testosterone with supplementation, 10.1% had data showing a decrease, 18.3% had data showing no change, and 61.5% had no data on testosterone at all.
• Median vitamin B12 content was about 1,291% of the recommended daily allowance, vitamin B6 about 808%, and zinc 272%. Thirteen products exceeded the FDA's upper intake limit for at least one ingredient (zinc, vitamin B3, or magnesium).

The limits: it was a snapshot of one search, and it judged ingredients against the literature, not finished products against each other. Still, it is the clearest picture available of the gap between the marketing and the research.

How big is a "small increase"?

Pooled results are often reported in ways that sound bigger than they are, so put them in context. A typical adult man's total testosterone falls somewhere between about 300 and 1,050 ng/dL (see what counts as normal), and the AUA uses 300 ng/dL as a reasonable cutoff for diagnosing deficiency. An average rise of about 60 ng/dL, the size of the largest averages below, would not move a man from clearly low to normal, and it says nothing about whether he would feel any different. Averages also hide the fact that some men in these trials rose and others didn't.

The reviews summarized here mainly report hormone levels, not symptoms. A man who feels bad needs a diagnosis, not a number that creeps up a little. See which symptoms actually track with low T.

Ingredient by ingredient

Ashwagandha

This is the ingredient with the most encouraging pooled data. A systematic review and meta-analysis of randomized, placebo-controlled trials (published 2026) pooled 23 trials with 1,706 people and found testosterone increased in men by an average of 57.43 ng/dL, but not in women. It also found lower cortisol and no change in estradiol, and suggested a possible dose-response relationship based on the active-compound content. The abstract didn't give a confidence interval for the testosterone figure, and it noted that heterogeneity and limited data warrant further standardized trials. The earlier 2021 review found that most of the evidence across herbs comes from young, non-clinical populations: 16 of 32 studies enrolled men under 40. Neither review establishes that ashwagandha helps men who actually have low testosterone. Safety is covered below.

Fenugreek

The most recent meta-analysis (published August 2026) covered 13 randomized placebo-controlled trials. Eight reported primary testosterone data in 637 randomized men, mostly healthy or resistance-trained men taking 500 to 600 mg a day for 8 to 12 weeks. Total testosterone was slightly higher with fenugreek (6 studies, 385 men; standardized mean difference 0.25, 95% CI 0.02 to 0.48), while free testosterone, the fraction your body can use, showed no clear change (5 studies, 334 men; 0.08, CI -0.48 to 0.63). The authors rated the certainty as very low and concluded that current evidence doesn't support testosterone-boosting claims. We covered it in our October 13 briefing.

Vitamin D

Vitamin D is the one with competing meta-analyses. A 2019 meta-analysis of 8 randomized trials found no significant effect on total testosterone (mean difference 0.20, 95% CI -0.20 to 0.60), including in subgroups by dose, duration, and baseline levels. A 2024 meta-analysis of 17 trials found a small increase (weighted mean difference 0.38, 95% CI 0.06 to 0.70, with substantial heterogeneity) and no effect on free testosterone. A 2026 meta-analysis found no clear effect on total testosterone (0.47 nmol/L, 95% CI -0.50 to 1.44, certainty rated low). Taken together, there is no reliable boost. Vitamin D still matters for bones and deficiency is common, so test first.

Zinc

Zinc is the clearest example of "correcting a deficiency, not boosting." In a 1996 study, four healthy young men whose zinc intake was restricted for 20 weeks saw testosterone fall from about 39.9 to 10.6 nmol/L. In the same paper, nine marginally zinc-deficient older men given zinc had testosterone rise from about 8.3 to 16.0 nmol/L. These were tiny studies, but they point the same way: zinc matters when you are short on it. Beyond that, more is not better, and the product study above found zinc content above the upper limit in some boosters.

D-aspartic acid and tribulus

In a randomized, placebo-controlled trial of resistance-trained men taking 3 g of D-aspartic acid a day during 28 days of heavy training, total and free testosterone did not change compared with placebo. For tribulus, a 2025 systematic review of 10 studies (483 participants, 400 to 750 mg a day for 1 to 3 months) found no significant androgen change in 8 of 10, mostly in men without low baseline testosterone. The two studies with rises were in men with low testosterone, and the increases were small (roughly 60 to 70 ng/dL). The authors concluded there is no robust evidence that tribulus raises testosterone.

Safety and quality

• Doses. Many boosters stack vitamins and minerals far above the recommended allowances, and some exceed upper limits (see above). High doses of zinc and some B vitamins aren't harmless.
• Ashwagandha and the liver. Case reports of ashwagandha-related liver injury exist. A 2023 review of reported cases (plus two new ones) notes most patients improved after stopping the supplement, while one earlier case ended in a liver transplant, and a 2026 review of drug-induced liver injury lists ashwagandha among recognized supplement causes and notes most patients recover after stopping. These cases are rare. See our supplements guide, and stop and call your doctor if you develop yellow eyes or skin, dark urine, or severe itching.
• Tainted products. Anything promising steroid-like results may contain ingredients not on the label. See SARMs and tainted products.
• Interactions and conditions. Supplements can interact with medications and aren't appropriate for everyone, including people with liver, kidney, heart, or thyroid conditions. Tell your clinician what you take.
• Fertility. The reviews above measured hormone levels, not sperm or fertility. If you're trying to conceive, don't assume a booster is harmless; see TRT and fertility.

What to do instead

1. Get tested. If you have symptoms, a morning blood test is how you find out whether testosterone is actually low. See getting tested, and consider checking vitamin D and zinc status at the same time.
2. Fix the levers with the strongest evidence. Sleep matters, and weight loss has solid evidence behind it. See sleep and testosterone, strength training after 40, and recovery.
3. Treat a deficiency if you have one. If vitamin D or zinc comes back low, correcting it is reasonable and cheap. That's treatment, not boosting.
4. If testosterone is truly low, the real options are medical. See the TRT guide, enclomiphene vs TRT, and our provider comparisons.
5. If you still want to try something, choose a single-ingredient product, ask the seller for the trial behind it, check the dose against the upper limits, and run it past your clinician.

Sources

1. Clemesha CG, Thaker H, Samplaski MK. "Testosterone boosting" supplements composition and claims are not supported by the academic literature. World J Mens Health. 2020;38(1):115-122. PubMed
2. Fornalik M, Malkiewicz A, Adamczak D, et al. Hormonal modulation with Withania somnifera: systematic review and meta-analysis of randomized-controlled trials. Planta Med. 2026;92(8):790-805. PubMed
3. Smith SJ, Lopresti AL, Teo SYM, Fairchild TJ. Examining the effects of herbs on testosterone concentrations in men: a systematic review. Adv Nutr. 2021;12(3):744-765. PubMed
4. Yang P, Niu Z, Guo J, et al. Effects of oral fenugreek-derived preparations on testosterone-related outcomes in adult men: a systematic review and meta-analysis of randomized placebo-controlled trials. Front Nutr. 2026;13. PubMed
5. Hosseini Marnani E, Mollahosseini M, Gheflati A, et al. The effect of vitamin D supplementation on the androgenic profile in men: a systematic review and meta-analysis of clinical trials. Andrologia. 2019;51(9):e13343. PubMed
6. Abu-Zaid A, Saleh SAK, Adly HM, et al. The impact of vitamin D on androgens and anabolic steroids among adult males: a meta-analytic review. Diseases. 2024;12(10):228. PubMed
7. Paez-Allendes L, Valenzuela-Fuenzalida JJ, Moya MP, et al. Vitamin D supplementation, total testosterone, and androgen bioavailability markers in adult men: a systematic review and meta-analysis of randomized controlled trials. Nutrients. 2026;18(13):2090. PubMed
8. Prasad AS, Mantzoros CS, Beck FW, et al. Zinc status and serum testosterone levels of healthy adults. Nutrition. 1996;12(5):344-348. PubMed
9. Willoughby DS, Leutholtz B. D-aspartic acid supplementation combined with 28 days of heavy resistance training has no effect on body composition, muscle strength, and serum hormones associated with the hypothalamo-pituitary-gonadal axis in resistance-trained men. Nutr Res. 2013;33(10):803-810. PubMed
10. Vilar Neto JO, et al. Effects of tribulus (Tribulus terrestris L.) supplementation on erectile dysfunction and testosterone levels in men: a systematic review of clinical trials. Nutrients. 2025;17(7):1275. PubMed
11. Bokan G, et al. Herb-induced liver injury by Ayurvedic ashwagandha as assessed for causality by the updated RUCAM: an emerging cause. Pharmaceuticals (Basel). 2023. PubMed; Björnsson ES. Common causes of drug-induced liver injury in 2025. Turk J Gastroenterol. 2026. PubMed
12. Mulhall JP, Trost LW, Brannigan RE, et al. Evaluation and management of testosterone deficiency: AUA guideline. J Urol. 2018;200(2):423-432. American Urological Association