Fertility Supplements: Evidence Ratings for Every Common Option

Fertility supplements: what the evidence actually shows

Supplements are the most heavily marketed part of fertility care and among the least well evidenced. Here is what the best available evidence says.

For men: the honest picture

A Cochrane systematic review of antioxidants for male subfertility pooled 90 randomised trials covering 10,303 subfertile men and 20 different antioxidants.

On live birth: antioxidants may increase live birth rates — odds ratio 1.43. Translated into plain numbers: if 16 out of 100 couples would have a baby without antioxidants, between 17 and 27 out of 100 would with them.

That sounds encouraging. Now the part that rarely appears in marketing:

> When studies at high risk of bias were removed from the analysis, there was no evidence of increased live birth.

The remaining eight better-quality trials showed an odds ratio of 1.22 with a confidence interval crossing no effect (0.85 to 1.75, P = 0.27). In other words, the apparent benefit was driven by the weakest studies.

The review authors rated the live birth evidence very low certainty, and concluded: subfertile couples should be advised that the current evidence is inconclusive based on serious risk of bias.

On clinical pregnancy: low-certainty evidence of an increase — from a baseline of about 15% to somewhere between 20% and 30%. Better certainty than the live birth finding, but pregnancy is not the outcome that matters most.

On semen parameters: the pooled analyses for motility and concentration were unreliable — heterogeneity between studies was extremely high.

On which antioxidant: there is insufficient evidence supporting any one type, dose, or combination over another. So even if you decide to take something, the evidence does not tell you what.

On downsides: no evidence of increased miscarriage risk. Antioxidants may cause more mild gastrointestinal discomfort — roughly 2% without, 2 to 7% with.

The AUA/ASRM guideline reaches a consistent position: the benefits of supplements are of questionable clinical utility in treating male infertility, and existing data are inadequate to recommend any specific agent.

What this means practically

Antioxidant supplements are cheap, low-risk, and possibly useless. If you want to take them, the harm is likely minimal and the cost modest. What you should not do is take them instead of getting assessed, or expect them to substitute for the measures that do have evidence: stopping smoking, moderating alcohol, reaching a healthier weight, treating chronic conditions, reducing heat exposure, and stopping testosterone or anabolic steroids.

Allow three months before judging any change — sperm production takes roughly 72 to 90 days.

For women

Folic acid is the clear exception and is not really a fertility supplement — at least 400 micrograms daily, started before conception, to reduce neural tube defect risk in the baby.

Vitamin D — correct a deficiency if you have one. Supplementing beyond that has not been shown to improve fertility outcomes.

Inositol in PCOS — evidence weaker than the marketing suggests. ESHRE (2026) recommends against myo-inositol in the IVF stimulation setting.

DHEA — ESHRE (2026) recommends against it before or during ovarian stimulation, in both low and normal responders, as a strong recommendation. Earlier signals of increased oocyte yield did not translate into more live births.

One caution

Most antioxidant supplements are uncontrolled by regulation, as the Cochrane authors note. Unregulated products have been found to contain undeclared ingredients — a particular concern with gym supplements, which are a recognised hidden source of anabolic steroids.

Tell your doctor everything you take.