Supplements
Selenium and male fertility
Selenium is essential in small amounts. Extra selenium has inconsistent semen evidence and a real toxicity risk.
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Short answer
Selenium is a trace element used in sperm antioxidant enzymes. Trials of selenium, sometimes with vitamin E, report mixed changes in semen parameters. They do not show a reliable improvement in pregnancy or live birth. Too much selenium is toxic. SemenBoost does not recommend selenium supplementation for fertility.
Key takeaways
- The gap between enough and too much is smaller than for many vitamins.
- Selenosis can cause hair loss, nail changes, nausea and fatigue.
- Combination products make it impossible to know which ingredient did what.
- Food sources in a varied diet are a different exposure from a high-dose capsule.
What it is
Selenium-dependent enzymes such as glutathione peroxidase are part of sperm antioxidant defence. Regions with very low soil selenium have had deficiency syndromes. That geography is not the same as a man in Britain or the United States adding 200 micrograms to an already selenium-containing diet.
Studies
Trials are small. Some report better motility or concentration when selenium is combined with vitamin E or other antioxidants. Others do not. Because the products are combinations, a positive result cannot be assigned to selenium. Cochrane’s class review remains the outcome context: very low-certainty live-birth evidence for antioxidants overall.
Safety
Chronic high intake causes selenosis. Brazil-nut binges plus a supplement are a realistic way to overshoot. People with thyroid disease should not add selenium casually, because selenium affects thyroid hormone metabolism. This page does not state a “studied fertility dose” as a target.
Evidence
Insufficient evidenceMixed, small, often combined-ingredient trials do not support a selenium fertility recommendation, and harm from excess is plausible.
Semen parameters
Some combination trials report semen-parameter changes. They are too entangled to credit selenium alone with a moderate rating.
Pregnancy and live birth
Live birth and pregnancy have not been reliably shown for selenium supplementation.
A change in a semen measurement is not the same finding as a pregnancy or a live birth.
Related
Sources
- Antioxidants for male subfertility — Cochrane, 2022
- Fertility problems: assessment and treatment (NG257) — NICE, 2026
How this page was prepared
Drafted with automated research assistance and checked against the cited primary sources. A named clinician has not reviewed this page. Medical review is pending. Changes to reference values are not published automatically.