Correcting a zinc shortfall raised testosterone in one small, uncontrolled study of older men. In small studies, restricting dietary zinc lowered testosterone in healthy young men, and correcting a marginal deficiency raised it in older men.1,2 In controlled trials of men who were not selected for deficiency, zinc taken with folic acid did not change serum testosterone.4,5 Your zinc status and a confirmed testosterone result tell you which group you are in, and that decides whether zinc has a job in your plan.
Zinc Deficiency and Lower Testosterone
The clearest human evidence comes from studies that removed zinc from the diet. A 1996 study restricted dietary zinc in four healthy young men. After 20 weeks, their mean serum testosterone fell from 39.9 to 10.6 nmol/L.1
A 1992 metabolic-ward study fed 11 young men controlled diets at several zinc levels. On the lowest zinc intake, their serum testosterone was lower than on the adequate intake (21.9 versus 26.9 nmol/L), and semen volume fell as well.2 The authors concluded that testosterone and semen volume are sensitive to short-term zinc depletion in young men.2
The same 1996 paper measured 40 men aged 20 to 80 and found that cellular zinc correlated with serum testosterone.1 It also stated that severe and moderate zinc deficiency is associated with hypogonadism, meaning low testosterone production, in men.1 Together, the restriction studies found that too little zinc lowers testosterone. They are deficiency studies, so the next question for you is whether your intake or level is low in the first place.
Correcting a Zinc Shortfall in Older Men
Restoring zinc in men who are short on it raised testosterone in one small study. The 1996 study gave zinc supplements to nine older men who were marginally zinc deficient. After six months, their mean serum testosterone rose from 8.3 to 16.0 nmol/L.1
That is a large change, and it comes from nine men with no placebo group. It shows what correcting a shortfall can do. It does not show that extra zinc helps a man whose zinc is already adequate.
If your diet is low in zinc or a lab shows you are deficient, correcting it is a reasonable step to discuss with your physician. If your zinc is already adequate, a supplement has no demonstrated testosterone effect to offer you.
Supplement Trials in Men Without a Known Deficiency
Controlled trials in men who were not chosen for zinc deficiency found no testosterone change. These trials paired zinc with folic acid and enrolled men from fertility clinics, so they speak most directly to that setting.
A 26-week double-blind trial gave 87 men, fertile and subfertile, either folic acid with zinc sulphate or placebo.4 Sperm concentration rose in the subfertile men, but testosterone and the other hormone measures did not change.4 The authors concluded that the sperm effect did not come from changes in FSH, testosterone or inhibin B.4
A 2017 meta-analysis of trials in subfertile men, seven studies in all, reached the same answer on hormones. Folate plus zinc showed no statistically different effect on serum testosterone compared with placebo.5
The largest trial, FAZST, randomized 2,370 men in couples planning infertility treatment to folic acid with zinc or placebo for six months.6 Live birth rates were nearly identical (34% versus 35%), and most semen measures did not differ.6 DNA fragmentation in sperm rose slightly with the supplement, and abdominal pain, nausea and vomiting were more common.6 The authors concluded that the findings do not support folic acid and zinc for male partners in infertility treatment.6
If you are taking zinc to raise a normal testosterone level, these trials give you no reason to expect a change. If fertility is your goal, raise it with your physician before you start any supplement, because the largest trial found no benefit.
The 2023 Review and Its Animal Evidence
The most positive summary of zinc and testosterone rests largely on animal research. A 2023 systematic review included 38 papers, of which 8 were clinical studies and 30 were animal studies.3 It concluded that zinc deficiency reduces testosterone and that supplementation improves it.3
The same review stated that the size of the effect may depend on baseline zinc and testosterone levels, the zinc form, the dose and the duration.3 Most of its evidence comes from animals. When you see a product promise more testosterone from zinc, ask whether the evidence behind it was in deficient men, replete men or animals.
Zinc Upper Limits and Copper Balance
Zinc has a ceiling, and going past it carries documented harms. A 2024 review on zinc toxicity lists the European Food Safety Authority's tolerable upper intake level as 25 mg per day, and gives 40 mg per day as the US limit.7
The review states that intake above recommended levels may cause anemia, neutropenia (low white blood cells) and zinc-induced copper deficiency.7 In the FAZST trial, gastrointestinal symptoms were more common in the supplement group.6
Count every source of zinc you take, including multivitamins and other supplements, before you add another. Your physician can weigh your total intake against these limits and decide whether a supplement makes sense for you.
Low Testosterone Assessment by a Physician
Low testosterone is a diagnosis made from labs and symptoms together. The American Urological Association (AUA) guideline states that care should focus on accurate assessment of total testosterone levels, symptoms and signs, with proper monitoring once treatment starts.8
One low reading is a starting point. Your physician confirms it, weighs the symptoms you report, and looks for the cause behind it. The low testosterone page covers the symptoms and how the diagnosis is made. If your levels are low and zinc is one of several factors, the plan addresses each of them in turn.
For the food side of the question, the testosterone food guide covers diet. For other supplements studied for testosterone, see testosterone supplements. The best supplements for men guide places zinc among the broader options. For booster products sold on this claim, see do testosterone boosters work.
The Opt Take on Zinc and Testosterone
Zinc is a correction for a shortfall, and it works best when you know you have one. Taking it blind to raise testosterone treats one possible cause without checking whether it is yours. Your physician reads the pattern across your labs to find which cause is yours.
At Opt Health, your initial panel covers 55+ biomarkers spanning hormones, inflammation, cardiovascular risk and more, taken at home or at a partner lab. A physician reviews the results with you 1:1 and reads your testosterone alongside your symptoms, history and other markers. Your plan can include prescriptions, peptides and supplements shipped from our pharmacy to your home.
Full labs and a physician consultation repeat every 3 to 4 months. Your physician compares each result with your baseline and adjusts the plan, which can mean adding zinc, removing it, or treating a different cause.
Get started: Begin with Opt Health, where a physician reads your labs, builds your plan, and adjusts it over the loop.
Frequently Asked Questions
Zinc takes part in over 300 enzymatic reactions in the body, along with gene regulation and immune function.7 In men, severe and moderate zinc deficiency is associated with low testosterone production.1 Short-term zinc depletion also lowered semen volume in young men on a controlled diet.2 Your physician can tell you whether your intake is likely to be adequate.
A zinc supplement is not necessary for every man. The testosterone benefit in human studies appeared in men who were zinc deficient.1 Trials in men who were not selected for deficiency found no change in testosterone.4,5 If your diet and labs show adequate zinc, you can skip it for testosterone purposes and focus on the cause your physician finds.
The documented harms of zinc supplements come from excess intake. A 2024 review lists an upper intake level of 25 mg per day from the European Food Safety Authority and gives 40 mg per day as the US limit.7 Excess intake may cause anemia, low white blood cells and copper deficiency.7 Tell your physician about every product containing zinc that you take.
Yes, too much zinc can cause harm. Intake above recommended levels may lead to zinc-induced copper deficiency, anemia and neutropenia.7 In the FAZST trial, men taking zinc with folic acid reported more abdominal pain, nausea and vomiting than men on placebo.6 Your physician can check your total intake and decide whether to adjust it.
Correcting a zinc shortfall raised testosterone in men in one small study without a placebo group. In nine marginally deficient older men, six months of zinc raised mean testosterone from 8.3 to 16.0 nmol/L.1 In men chosen without regard to zinc status, zinc combined with folic acid did not change testosterone, and the largest trial found no fertility benefit.4-6 Your labs show which of these groups you fall into.
Knowing whether zinc matters for you starts with your own labs. An Opt Health membership pairs 55+ biomarkers with a 1:1 physician review, then repeats labs and a physician consultation every 3 to 4 months.
References
- Prasad AS et al. Zinc status and serum testosterone levels of healthy adults. Nutrition. 1996;12(5):344-348. https://pubmed.ncbi.nlm.nih.gov/8875519/
- Hunt CD et al. Effects of dietary zinc depletion on seminal volume and zinc loss, serum testosterone concentrations, and sperm morphology in young men. Am J Clin Nutr. 1992;56(1):148-157. https://pubmed.ncbi.nlm.nih.gov/1609752/
- Te L et al. Correlation between serum zinc and testosterone: a systematic review. J Trace Elem Med Biol. 2023;76:127124. https://pubmed.ncbi.nlm.nih.gov/36577241/
- Ebisch IM et al. Does folic acid and zinc sulphate intervention affect endocrine parameters and sperm characteristics in men? Int J Androl. 2006;29(2):339-345. https://pubmed.ncbi.nlm.nih.gov/16533356/
- Irani M et al. The effect of folate and folate plus zinc supplementation on endocrine parameters and sperm characteristics in sub-fertile men: a systematic review and meta-analysis. Urol J. 2017;14(5):4069-4078. https://pubmed.ncbi.nlm.nih.gov/28853101/
- Schisterman EF et al. Effect of folic acid and zinc supplementation in men on semen quality and live birth among couples undergoing infertility treatment: a randomized clinical trial. JAMA. 2020;323(1):35-48. https://pubmed.ncbi.nlm.nih.gov/31910279/
- Schoofs H et al. Zinc toxicity: understanding the limits. Molecules. 2024;29(13). https://pubmed.ncbi.nlm.nih.gov/38999082/
- Mulhall JP et al. Evaluation and management of testosterone deficiency: AUA guideline. J Urol. 2018;200(2):423-432. https://pubmed.ncbi.nlm.nih.gov/29601923/
This content is for informational purposes and does not replace evaluation, diagnosis, or treatment by a qualified medical professional.
This article is part of our guide to testosterone. See how physician-managed TRT works at Opt Health.
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