Vitamin D is a fat-soluble vitamin your skin makes when exposed to the sun's UVB rays; smaller amounts come from oily fish, egg yolks and fortified foods. Authorised UK and EU health claims state that vitamin D contributes to the maintenance of normal bones, to the maintenance of normal muscle function and to the normal function of the immune system. Your level is checked with a blood test for 25-hydroxyvitamin D, usually reported in nmol/L in the UK.
Animal and population studies have suggested a role for vitamin D in male reproduction3, and randomised trials have tested whether supplements change hormones and semen. A 2024 meta-analysis of 17 randomised trials found that vitamin D supplementation raised total testosterone in adult men2.
Does vitamin D increase testosterone?
Pooled trials show a rise in total testosterone with vitamin D supplements. Other hormones, including free testosterone, did not change significantly, and results have varied between studies.
The 2024 meta-analysis of 17 randomised trials found that supplementation raised total testosterone, with variation between studies. Free testosterone, SHBG, LH, FSH and oestradiol did not change significantly, and the authors called for further well-designed trials2.
Results depend partly on who is studied. In a 12-week double-blind trial of 98 healthy men with normal testosterone and vitamin D levels below 75 nmol/L, vitamin D3 (the trial used 20,000 IU a week) did not change total testosterone compared with placebo1.
Correcting a low vitamin D level is sensible for your bones and general health. If you have low energy, low sex drive or fewer morning erections, ask for your testosterone to be tested so a doctor can check for hypogonadism.
What have studies found on vitamin D and fertility?
In a trial of infertile men with low vitamin D, those with low sperm counts had a higher live birth rate with supplements. The researchers have called for this to be confirmed by others.
In a triple-blind trial, 330 infertile men with vitamin D levels of 50 nmol/L or lower received either a single high dose of vitamin D followed by daily vitamin D and calcium for 150 days, or placebo. In men with low sperm counts, the live birth rate was 35.6% with vitamin D versus 18.3% with placebo, and spontaneous pregnancies tended to be more common in the vitamin D group overall. Standard semen measures did not differ between the groups3.
For the everyday factors that affect fertility, see our guide to lifestyle factors and male fertility.
Can you take too much vitamin D?
Yes. Toxicity is rare but can be serious, and usually comes from taking very high doses for a long time.
Vitamin D toxicity causes high blood calcium (hypercalcaemia). Typical symptoms include confusion, vomiting, abdominal pain, thirst, passing a lot of urine and dehydration. Blood levels of 25-hydroxyvitamin D above 375 nmol/L are the hallmark of overdosing, and some people react to much lower doses because of how their body handles vitamin D4.
Stick to the amount on the label or the one your doctor recommends. Talk to a doctor before taking high-dose vitamin D if you have sarcoidosis or another granulomatous condition, which can raise active vitamin D levels on their own4, or if you take regular prescription medicine.
Common questions
Will vitamin D raise my testosterone if I'm deficient?
Pooled trials found a rise in total testosterone with vitamin D supplements2, and results have varied between studies and groups of men. Symptoms of low testosterone need proper assessment, including a blood test.
How long did vitamin D trials run?
Trials looking at testosterone and fertility ran from 12 weeks1 to 150 days3. Any effect on sperm takes time to show because sperm develop over weeks; see how long sperm take to regenerate.
Should I get my vitamin D tested?
If you have symptoms, risk factors for deficiency or are thinking about high-dose supplements, a GP can arrange a 25-hydroxyvitamin D blood test. Measuring your level is also how doctors identify vitamin D toxicity4.
Read more on this
Supplement ingredients for men’s sexual health: what the research shows
How testosterone changes after 40 (and what actually helps)
Lifestyle factors that affect male fertility: a practical guide
Sources
- Lerchbaum E, et al. Vitamin D and Testosterone in Healthy Men: A Randomized Controlled Trial. J Clin Endocrinol Metab. 2017;102(11):4292-4302. PubMed
- Abu-Zaid A, et al. The Impact of Vitamin D on Androgens and Anabolic Steroids among Adult Males: A Meta-Analytic Review. Diseases. 2024;12(10):228. PubMed
- Blomberg Jensen M, et al. Effects of Vitamin D Supplementation on Semen Quality, Reproductive Hormones, and Live Birth Rate: A Randomized Clinical Trial. J Clin Endocrinol Metab. 2018;103(3):870-881. PubMed
- Marcinowska-Suchowierska E, et al. Vitamin D Toxicity-A Clinical Perspective. Front Endocrinol (Lausanne). 2018;9:550. PubMed
Not medical advice. Written by Eric Stephens from the research cited above; not reviewed by a doctor. If something worries you, see a GP.