Vitamin D and Fertility
Vitamin D receptors are expressed in ovaries, endometrium, testes, and sperm cells, and calcitriol regulates key genes in reproductive tissues. Deficiency correlates with subfertility in both sexes; supplementation shows modest, condition-specific benefit — clearest in PCOS and in some IVF cohorts.
IVF outcomes
Multiple meta-analyses (Chu 2018; Zhao 2019) find women with sufficient 25(OH)D (≥ 30 ng/mL) at IVF cycle start had higher clinical pregnancy rates (RR ~1.34) and live birth rates (RR ~1.33) than women with deficient or insufficient levels. The 2023 Cochrane review flagged the evidence as low certainty pending well-powered RCTs, but the signal is consistent enough that many reproductive endocrinologists correct deficiency pre-cycle.
Female subfertility mechanisms
- AMH regulation in granulosa cells (vitamin D increases AMH gene expression)
- Endometrial receptivity and HOXA10 expression
- Immune tolerance at the maternal-fetal interface
- Insulin sensitivity — particularly relevant in PCOS
Male fertility
The 307-man Blomberg-Jensen (2018) trial gave cholecalciferol + calcium to infertile men and showed modest improvements in sperm motility and DNA fragmentation vs placebo, though the live birth endpoint was not significantly different. Meta-analyses find lower 25(OH)D in men with abnormal semen parameters than in normal controls. Correcting deficiency is a reasonable low-cost step in male-factor workup.
PCOS and ovulation induction
Vitamin D + metformin combinations improve ovulation frequency and clomiphene response in PCOS. See our PCOS page for full details.
Pre-conception dosing
- Both partners test 25(OH)D as part of the fertility workup.
- Correct any deficiency 3+ months before attempted conception or IVF.
- Target ≥ 30 ng/mL; some fertility clinics aim 40–60.
- Cholecalciferol 2,000–4,000 IU/day is a safe pre-conception dose for both sexes.
- Continue through pregnancy — see pregnancy page.