Does zinc boost testosterone and male fertility?

Not in the trials that measured it. A 2017 meta-analysis of randomized trials in sub-fertile men found that folate plus zinc left serum testosterone no different from placebo (P = .86). For fertility, the largest trial gave 30 mg of zinc and 5 mg of folic acid a day to the men of 2370 couples for 6 months, and live births came to 34% against 35% on placebo. Zinc does matter when there is too little of it. Eleven young men who ate only 1.4 mg a day for 35 days saw their testosterone fall.

Myth. Zinc tablets as a testosterone booster were tested in sub-fertile men taking zinc with folate, and pooled trials found no difference from placebo. A 2024 review of 27 marketed testosterone boosters, with 5 of its 52 studies on zinc or magnesium, found that most fail to raise total testosterone.

Unsettled. One narrower question is still open. No meta-analysis we found has pooled testosterone for zinc taken alone by men with normal zinc levels, so the null result above comes from men who also took folate.

What the trials found

Testosterone

The direct answer is the 2017 meta-analysis above. Folate plus zinc raised sperm concentration and normal morphology in sub-fertile men, and it did not move serum testosterone, inhibin B or FSH. The abstract gives no absolute differences, and heterogeneity across the trials was high.

Where zinc did raise testosterone, the men were ill. A Cochrane review of people with chronic kidney disease found that oral zinc raised end-of-treatment testosterone in 1 trial of 20 patients, a standardized difference of 1.62 (95% CI 0.58 to 2.66). Zinc added to the dialysis fluid did not, in 2 trials of 22 patients. One small trial in kidney patients does not transfer to healthy men.

The other direction is clearer. On a metabolic ward, 11 young men ate 10.4 mg of zinc a day in one period and 1.4 mg in another. On the low intake, serum testosterone was 21.9 nmol/L against 26.9, and semen volume was 0.45 tsp (2.24 mL) against 3.30. A 2023 systematic review of 8 clinical and 30 animal studies drew the same line. Its authors concluded that zinc deficiency lowers testosterone, and that any effect of supplements depends on starting zinc and testosterone levels, the form, the dose and the duration. Most of the studies in that review were in animals, and it pooled nothing.

Sperm counts

A 2018 meta-analysis of randomized trials found zinc raised sperm concentration by 1.48 million per mL (95% CI 0.69 to 2.27) and total motility by 7.03 percentage points (95% CI 6.03 to 8.03). The authors themselves point to small samples and high heterogeneity, and the analysis has nothing on testosterone. Infertile men have less zinc in their seminal fluid than fertile men. Across 20 case-control studies with 2600 cases and 867 controls the standardized difference was -0.64 (95% CI -1.01 to -0.28). That is an association, and it does not show that low zinc caused the infertility.

Pregnancies and live births

This is the outcome couples care about, and here the answer is no gain. A 2025 meta-analysis of 50 placebo-controlled trials lasting at least 12 weeks found no effect of any dietary supplement on pregnancy or live birth. Zinc with folic acid improved sperm concentration only, and the certainty of the evidence was low or very low. FAZST, the trial in the chart, is the largest single test. The SUMMER trial of 1171 men gave a daily antioxidant tablet containing 10 mg of zinc for 6 months, and ongoing pregnancies came to 33.8% against 37.5% on placebo, which did not reach significance. Zinc was one ingredient among several there, so its own share cannot be pulled out.

A 2019 review of 18 placebo-controlled trials called 66 mg of zinc a day with 5 mg of folic acid promising for male infertility. That was the authors' reading of the trials, not a pooled estimate, and the dose sits above the 40 mg adult upper limit.

Who should be careful

Not for everyone. In FAZST, men on 30 mg zinc with 5 mg folic acid had slightly more sperm DNA fragmentation than on placebo, 29.7% against 27.2% (mean difference 2.4%, 95% CI 0.5% to 4.4%). They also had more abdominal discomfort (6% against 3%), nausea (4% against 2%) and vomiting (3% against 1%). The trial gave both nutrients together, so it cannot say which one did this.

Dose is the second caution. NIH sets the adult upper limit for zinc at 40 mg a day. It says 50 mg or more over weeks can inhibit copper absorption, reduce immune function and lower HDL cholesterol, and that this much is unlikely to come from food alone. The 66 mg regimen called promising in the 2019 review is above that limit. If you have kidney disease, the one group where oral zinc raised testosterone in a trial, whether and how much zinc to take is a question for the person treating you.

What expert bodies say

The NIH zinc fact sheet sets the upper limit above and warns about copper. It had nothing on testosterone when we searched it, and we found no guideline that recommends zinc to raise testosterone or to improve male fertility.

If you eat a normal diet, the trials give no reason to expect a zinc tablet to raise your testosterone or help you conceive.

How we searched

What would change this answer

• A placebo-controlled trial of zinc alone, with serum testosterone as the main outcome, in men with normal zinc levels. We found none, and no meta-analysis has pooled that question.
• The same trial in men with measured low zinc, which is where the depletion experiment and the review of 38 studies point.
• Hormone results from FAZST, if the full text reports them, and a trial that separates zinc from folic acid for the rise in sperm DNA fragmentation.
• A registered trial now running. ClinicalTrials.gov had none for zinc and testosterone when we searched.

Sources

1. ev-znt-01 · Meta-analysis or systematic review · systematic review and meta-analysis of randomized controlled trials · n = 7 studies, 6 meta-analyzed
   Folate plus zinc supplementation did not show any statistically different effect on serum testosterone (P = .86), inhibin B (P = .84), FSH (P = .054), and sperm motility (P = .169) as compared to the placebo.
   
   Who: sub fertile men with semen analyses, who took oral folic acid or folate plus zinc
   Effect: serum testosterone P = .86 vs placebo; inhibin B P = .84; FSH P = .054; sperm concentration and morphology P < .001
   Certainty: Directly about testosterone: zero effect in subfertile men. Heterogeneity is high, the abstract gives no absolute differences.
   Urol J, 2017 · checked 2026-10-07 · we read the abstract
2. ev-znt-02 · Meta-analysis or systematic review · Cochrane systematic review and meta-analysis of RCTs and quasi-RCTs · n = 15 studies, 352 patients overall; zinc testosterone outcomes 1 study of 20 and 2 studies of 22
   End of treatment testosterone levels were not significantly increased by addition of zinc to dialysate (2 studies, 22 patients, MD 0.21 ng/mL, 95% CI -2.14 to 2.55) but oral zinc improved end of treatment testosterone levels (1 study, 20 patients, SMD 1.62, 95% CI 0.58 to 2.66).
   
   Who: patients with chronic kidney disease (predialysis, dialysis and kidney transplant)
   Effect: oral zinc SMD 1.62 (95% CI 0.58 to 2.66); dialysate zinc MD 0.21 ng/mL (95% CI -2.14 to 2.55)
   Certainty: Group with typical zinc deficiency (dialysis); one small RCT. Does not transfer to healthy men.
   Cochrane Database Syst Rev, 2010 · checked 2026-10-07 · we read the abstract
3. ev-znt-03 · Meta-analysis or systematic review · systematic review and meta-analysis of randomized clinical trials · n = 28 articles, 15 meta-analyzed
   Total sperm concentrations [expressed as mean differences (MDs); 95% CIs, in spermatozoa (spz)/mL] were increased by selenium (3.91 × 106 spz/mL; 3.08, 4.73 spz/mL), zinc (1.48 × 106 spz/mL; 0.69, 2.27 spz/mL), omega-3 (n-3) fatty acids (10.98 × 106 spz/mL; 10.25, 11.72 spz/mL), and coenzyme Q10 (CoQ10) (5.93 × 106 spz/mL; 5.36, 6.51 spz/mL).
   
   Who: men in randomized clinical trials of nutrients, dietary supplements or food and sperm quality
   Effect: sperm concentration MD 1.48 x10^6/mL (95% CI 0.69 to 2.27); total motility MD 7.03% (95% CI 6.03% to 8.03%)
   Certainty: The authors themselves write about small samples and considerable heterogeneity; there are no data on testosterone.
   Adv Nutr, 2018 · checked 2026-10-07 · we read the abstract
4. ev-znt-04 · Meta-analysis or systematic review · systematic review and meta-analysis of randomized controlled trials with GRADE · n = 50 studies
   No effect on pregnancy and live birth was found. Different supplements improved single sperm parameters: Zinc and folic acid and ≥3 substance dietary supplements improved sperm concentration, selenium, carnitine, and coenzyme Q10 improved motility and alpha-lipoic acid improved normal morphology.
   
   Who: men with infertility in randomized controlled trials with treatment durations of 12 weeks or more versus placebo
   Effect: no effect on pregnancy and live birth; zinc and folic acid improved sperm concentration; GRADE certainty generally low or very low
   Certainty: The newest synthesis (search to May 2024), includes FAZST. Main conclusion: no convincing evidence for any supplement.
   Nutrients, 2025 · checked 2026-10-07 · we read the abstract
5. ev-znt-05 · Meta-analysis or systematic review · systematic review and meta-analysis of randomized double-blind placebo-controlled trials · n = 18 trials
   The systematic review identified promising data for supplementation with 66 mg/day zinc combined with folic acid (5 mg/day), and the polyunsaturated fatty acids eicosapentaenoic acid (EPA; 1.12 g/day) and docosahexaenoic acid (DHA; 0.72 g/day).
   
   Who: men with infertility in randomized, double-blind, placebo-controlled trials
   Effect: zinc 66 mg/day plus folic acid 5 mg/day rated promising in the systematic review part, not pooled
   Certainty: For zinc, only the qualitative conclusion of the review part, without pooling. The dose 66 mg > UL 40 mg (ev-znt-10); FAZST with 30 mg did not confirm benefit.
   Reprod Biomed Online, 2019 · checked 2026-10-07 · we read the abstract
6. ev-znt-06 · Randomized controlled trial(s) · multicenter randomized placebo-controlled clinical trial · n = 2370 couples
   Live birth was not significantly different between treatment groups (404 [34%] in the folic acid and zinc group and 416 [35%] in the placebo group; risk difference, -0.9% [95% CI, -4.7% to 2.8%]).
   
   Who: Couples (n = 2370; men aged ≥18 years and women aged 18-45 years) planning infertility treatment
   Effect: live birth 404 (34%) vs 416 (35%); risk difference -0.9% (95% CI -4.7% to 2.8%)
   Certainty: The largest RCT on the topic; 75% reached the visit at 6 months. Testosterone was not the primary outcome.
   JAMA, 2020 · checked 2026-10-07 · we read the abstract
7. ev-znt-07 · Randomized controlled trial(s) · multicenter randomized placebo-controlled clinical trial · n = 2370 men randomized
   A statistically significant increase in DNA fragmentation was observed with folic acid and zinc supplementation (mean of 29.7% for percentage of DNA fragmentation in the folic acid and zinc group and 27.2% in the placebo group; mean difference, 2.4% [95% CI, 0.5% to 4.4%]). Gastrointestinal symptoms were more common with folic acid and zinc supplementation compared with placebo (abdominal discomfort or pain: 66 [6%] vs 40 [3%], respectively; nausea: 50 [4%] vs 24 [2%]; and vomiting: 32 [3%] vs 17 [1%]).
   
   Who: men of couples planning infertility treatment, 30 mg elemental zinc and 5 mg folic acid daily for 6 months
   Effect: DNA fragmentation MD 2.4% (95% CI 0.5% to 4.4%); abdominal discomfort 6% vs 3%, nausea 4% vs 2%, vomiting 3% vs 1%
   Certainty: Axis 6: adverse effects at a dose of 30 mg (below the UL). The contribution of zinc and folic acid is not separated.
   JAMA, 2020 · checked 2026-10-07 · we read the abstract
8. ev-znt-08 · Randomized controlled trial(s) · randomized-order controlled depletion trial on a metabolic ward · n = 11
   Compared with when they were consuming 10.4 mg Zn/d, volunteers consuming 1.4 mg Zn/d exhibited decreased semen volumes (3.30 vs 2.24 mL) and serum testosterone concentrations (26.9 vs 21.9 nmol/L), and no change in seminal zinc concentrations.
   
   Who: Eleven volunteers living on a metabolic ward
   Effect: serum testosterone 26.9 vs 21.9 nmol/L and semen volume 0.67 vs 0.45 tsp (3.30 vs 2.24 mL) at 1.4 vs 10.4 mg Zn/d
   Certainty: Shows the mechanism "deficiency lowers testosterone," not "supplement raises it above normal." Very small sample.
   Am J Clin Nutr, 1992 · checked 2026-10-07 · we read the abstract
9. ev-znt-09 · Randomized controlled trial(s) · multicenter double-blind placebo-controlled randomized clinical trial · n = 1171 men
   Ongoing pregnancy rate within 6 months was not significantly different between the 2 groups (193 of 571 [33.8%] vs 208 of 555 [37.5%]; adjusted odds ratio [AOR], 0.85 [95% CI, 0.66-1.09]; P = .20).
   
   Who: men aged 18 to 50 years with female partners aged 18 to 43 years, who sought fertility care
   Effect: ongoing pregnancy 193/571 (33.8%) vs 208/555 (37.5%); AOR 0.85 (95% CI 0.66-1.09)
   Certainty: A multicomponent tablet (betaine, L-cystine, B vitamins, 10 mg zinc); the effect of zinc is not singled out.
   JAMA Netw Open, 2025 · checked 2026-10-07 · we read the abstract
10. ev-znt-10 · Position of an expert body · agency fact sheet · n = —
    Doses of 50 mg of zinc or more over a period of weeks can inhibit copper absorption, reduce immune function, and lower high-density lipoprotein cholesterol levels; however, it is unlikely that a person would obtain this much zinc from food alone. The Tolerable Upper Intake Level for zinc is 40 mg for adults, and it ranges from 4 to 34 mg for infants, children, and adolescents, depending on age.
    
    Who: General population, NIH Office of Dietary Supplements zinc fact sheet
    Effect: UL 40 mg/day for adults; 4 to 34 mg for infants, children and adolescents; >=50 mg/day for weeks impairs copper absorption
    Certainty: Authority position (E): upper limit and harm from 50 mg and above over weeks.
    NIH Office of Dietary Supplements, Zinc fact sheet for health professionals · checked 2026-10-07 · we read the section
11. ev-znt-11 · Observational data · systematic review without meta-analysis · n = 52 studies
    Our findings indicate that most fail to increase total testosterone.
    
    Who: male athletes, men with late-onset hypogonadism, infertile men and healthy men
    Effect: most boosters did not increase total testosterone; no pooled estimate
    Certainty: The quote says only "most fail", without a separate verdict on zinc; no quantitative synthesis.
    Int J Impot Res, 2024 · checked 2026-10-07 · we read the abstract
12. ev-znt-12 · Observational data · systematic review of clinical and animal studies, no meta-analysis · n = 38 papers
    Furthermore, the effect degree of zinc on serum testosterone may vary depending on basal zinc and testosterone levels, zinc dosage form, elementary zinc dose, and duration.
    
    Who: 38 papers including 8 clinical and 30 animal studies
    Effect: direction only: deficiency lowers, supplementation raises testosterone; modified by baseline status, dose form, elemental dose and duration
    Certainty: Most of those included are animals; the conclusion "the supplement raises it" rests on 8 clinical studies without a pool. An important caveat about baseline status.
    J Trace Elem Med Biol, 2023 · checked 2026-10-07 · we read the abstract
13. ev-znt-13 · Observational data · meta-analysis of case-control studies · n = 20 studies; 2,600 cases and 867 controls
    Our meta-analysis results indicated that the seminal plasma zinc concentrations from infertile males were significantly lower than those from normal controls (SMD (standard mean differences) [95% CI] -0.64 [-1.01, -0.28]).
    
    Who: infertile males and normal controls
    Effect: seminal plasma zinc SMD -0.64 (95% CI -1.01 to -0.28) in infertile vs fertile men
    Certainty: Association, not causality; level C by comparison design.
    Sci Rep, 2016 · checked 2026-10-07 · we read the abstract