Does Vitamin D Increase Testosterone?

No — vitamin D does not raise testosterone. Two randomized, placebo-controlled trials from the same research group in Graz, Austria tested exactly this: one in men with normal testosterone, one in men with low testosterone. Both came back null, and so did the subgroup with the lowest vitamin D inside the second one. Two meta-analyses of the wider literature agree. The belief survives because low vitamin D genuinely does track with low testosterone in population data, and because the biology behind the idea is elegant. Neither of those is an effect.

The short answer

Vitamin D supplementation has not been shown to raise testosterone in men. The strongest evidence is two double-blind, placebo-controlled trials that gave men 20,000 IU of vitamin D3 a week for 12 weeks and measured total testosterone by mass spectrometry. In 98 men with normal testosterone, there was no significant treatment effect.² In 94 men with low testosterone, the between-group difference was −0.188 nmol/L (95% CI −1.50 to 1.12, p = 0.776) — and every secondary hormone measure was null too.¹ Pooled analyses of the wider trial literature find the same thing.³⁴

That grade covers every group tested so far: men with normal testosterone, men with low testosterone, and the lowest-vitamin-D subgroup inside those trials. It is worth being precise about what a D means here. This is not "nobody has looked." It is "people have looked, repeatedly, with good methods, and found nothing" — which is a different and more useful kind of D.

What the randomized trials found

Almost every article on this question leads with the observational association and the mechanism, then mentions the trials near the bottom. That ordering is backwards. Here are the trials first.

The trial in men with normal testosterone (2017)

The Graz Vitamin D&TT-RCT ran at the Medical University of Graz from December 2012 to January 2017. Ninety-eight healthy men completed it, all with total testosterone at or above 10.4 nmol/L and 25-hydroxyvitamin D below 75 nmol/L. Mean age was 39 (±13), mean 25(OH)D 53.3 nmol/L (±18.3), mean total testosterone 19.1 nmol/L (±5.6). Fifty men got 20,000 IU of vitamin D3 a week and fifty got placebo, for 12 weeks, double-blind, with testosterone measured by mass spectrometry as the primary outcome.²

The result: "no significant treatment effect on TT was found." The median change in the vitamin D group was 0.5 nmol/L (P = 0.497).²

One secondary finding is worth reporting because nobody else does. The trial also tracked insulin sensitivity, and the vitamin D group's quantitative insulin sensitivity check index (QUICKI) fell by a median of 0.02 (P = 0.034) — a decrease, meaning slightly worse insulin sensitivity — with a non-significant trend the same way on the Matsuda index (−0.9, P = 0.051).² Read that carefully rather than dramatically: it was one of a long list of secondary outcomes, the kind of result that surfaces by chance when you measure many things at once, and the authors concluded that more study is needed, not that vitamin D harms metabolism.² It isn't a reason to avoid vitamin D. It's a reason to notice that this trial's one significant hormone-adjacent result pointed the wrong way.

The trial in men with low testosterone (2019)

This is the one that closes the argument, and it is the paper most consumer pages either miss or merge with the 2017 trial. Same group, same protocol, different men. Between March 2013 and November 2017, 100 men with total testosterone below 10.4 nmol/L and 25(OH)D below 75 nmol/L were randomized; 94 completed. Mean age was 47 (±12), mean 25(OH)D 56.3 nmol/L (±18.3). Again 20,000 IU of vitamin D3 a week versus placebo for 12 weeks.¹

Total testosterone: no effect. The between-group difference at 12 weeks was −0.188 nmol/L (95% CI −1.50 to 1.12), p = 0.776.¹ The secondaries went the same way — free testosterone p = 0.827, sex hormone-binding globulin p = 0.197, free androgen index p = 0.371, estradiol p = 0.651.¹ The published conclusion is one sentence: "Vitamin D treatment had no effect on serum TT levels in middle-aged healthy men with low TT levels."¹

And now the detail that matters most on this page. The investigators ran a subgroup analysis in the 39 men whose baseline 25(OH)D was below 50 nmol/L — the threshold the NIH's expert committee treats as inadequate.⁶ In that subgroup, total testosterone still showed no treatment effect: −0.472 nmol/L (95% CI −3.18 to 2.23), p = 0.725.¹

That is the escape hatch every other page leaves open — closed as far as anyone has looked. Our usual framing across supplements — correcting a shortfall can help, topping up when you're already replete does nothing — is a good rule, and it holds for several nutrients; zinc is the usual example. It does not hold here, and we won't smooth the two into a matching answer for the sake of consistency. Two nutrients, two bodies of evidence, two conclusions.

The strongest objection to our own conclusion

Three limitations, stated plainly, because a page that prints only the convenient half of a study doesn't deserve to be believed.

The men weren't as low-testosterone as the entry criterion suggests. Screening used a routine immunoassay; the researchers then re-measured the stored samples with isotope-dilution mass spectrometry, the better method. Baseline median total testosterone read 8.2 nmol/L by immunoassay but 12.7 nmol/L by mass spectrometry.¹ By the better assay, the group's median sat comfortably above the 10.4 nmol/L cut-off they were enrolled under — so the cohort was less uniformly low-testosterone than "men with low testosterone" implies.

Nobody has tested frankly deficient men. The NIH puts the deficiency threshold at 25(OH)D below 30 nmol/L; 30 to under 50 nmol/L is "potentially at risk of inadequacy," and 50 nmol/L or more is sufficient for most people.⁶ Both trials averaged 53.3 and 56.3 nmol/L — the sufficient band. The subgroup that got closest used the under-50 line, not under-30. No trial has enrolled only severely deficient men, so strictly speaking that scenario is untested.

The subgroup was tiny and unplanned. Those 39 men were 19 on vitamin D against 20 on placebo, and the authors state the subgroup analyses were not pre-specified.¹ A null in 39 men is weak evidence of absence on its own.

What keeps the conclusion standing despite all three is that it doesn't rest on that subgroup alone — the pooled evidence below tested the same question across the whole literature and got the same answer.

What the meta-analyses found

Two independent pooled analyses, seven years apart, agree.

The most recent is a 2026 systematic review and meta-analysis in Nutrients. It retained 27 reports for qualitative synthesis and considered 18 of them candidates for pooling, which became 21 comparison-level records — but the primary total-testosterone model drew on 11 comparisons, and that's the number the headline result belongs to. Result: mean difference 0.47 nmol/L (95% CI −0.50 to 1.44), I² = 24.1% — no clear effect. SHBG (MD 0.27), free androgen index (MD −0.37), and calculated free testosterone (MD −0.0096) were all null as well, and GRADE certainty was rated low for testosterone, SHBG, and the free androgen index.³ The authors' conclusion: current randomized evidence "does not demonstrate a statistically clear or reproducible effect of vitamin D supplementation on total testosterone or androgen bioavailability markers in adult men."³

Two honest qualifiers. The confidence interval runs up to 1.44 nmol/L, so a modest rise isn't mathematically excluded — nothing in the data points to one, but "no clear effect" is not proof of zero. And the review team couldn't search Embase because institutional access was unavailable, an amendment they declare openly.³

The earlier meta-analysis, published in Andrologia in 2019, pooled eight studies yielding 10 effect sizes, across doses from 600 IU a day to 60,000 IU a week and durations from six weeks to 36 months. Total testosterone: MD 0.20 (95% CI −0.20 to 0.60, p = 0.336). SHBG: MD 1.56 (95% CI −0.85 to 3.97, p = 0.204).⁴ The load-bearing part is what happened when the authors cut the data: subgroup analyses by duration, by daily versus weekly dosing, by dosing frequency, and by baseline vitamin D level and baseline testosterone level all showed no significant effect on testosterone.⁴ Their verdict was that the analysis "did not find any evidence to support beneficial effect of vitamin D supplementation on TT and SHBG in men."⁴

Sliced by how low your vitamin D was to start with, and by how low your testosterone was to start with, it still comes out to nothing.

Then why does low vitamin D track with low testosterone?

Because vitamin D status isn't random, and neither is who has it.

The NIH's own fact sheet lists who runs low. People with a BMI of 30 or more have lower serum 25(OH)D — not because obesity impairs the skin's ability to make vitamin D, but because greater amounts of subcutaneous fat sequester more of the vitamin. Older adults run low because skin synthesis declines with age and they spend more time indoors. So do people whose work, clothing, or housing limits sun exposure — and UVB doesn't penetrate glass, so a sunny office window contributes nothing.⁶

Look at that list again. It is largely a description of being heavier, older, less mobile, and indoors — circumstances that carry plenty of their own consequences for how a body runs. When a cross-sectional study finds low vitamin D sitting next to low testosterone, the most economical explanation is that both are downstream of the same life, not that one causes the other. That's the reading the reviews in this area arrive at: observational studies suggest an association, and the randomized trials that can separate cause from company keep failing to find an effect.⁵³

Randomization is what breaks the tie. It hands vitamin D out by coin flip, so the only systematic difference between the two groups is the capsule. Do that, and the association evaporates.

The mechanism is real. It just doesn't cash out.

The hypothesis was never silly. Vitamin D receptor expression and vitamin D-metabolizing enzymes have been identified in tissues well beyond bone, including parts of the male reproductive tract³ — which is exactly the kind of finding that makes a trial worth running.

Then the trials ran. The most-cited review of this literature carries the verdict in its own title: Mechanistically Dazzling but Clinically Disappointing. Its conclusion, verbatim: "Mechanistically, vitamin D exhibits essential roles in the testis and prostate; otherwise, there is no apparent evidence to support the use of vitamin D supplementation to increase testosterone levels and to improve clinical outcomes related to the male reproductive system."⁵ The same review notes that most randomized trials of vitamin D and testosterone "have failed to detect any significant effect."⁵

A receptor in a tissue tells you a question is worth asking. It doesn't tell you the answer.

Should you take vitamin D anyway?

Possibly — just not for this.

Vitamin D has real, well-established roles in the body, and a genuine shortfall is worth finding and fixing. That case is independent of testosterone and doesn't get weaker because this particular claim didn't hold up. For reference, the recommended dietary allowance is 15 mcg (600 IU) a day for adults 19 to 70 and 20 mcg (800 IU) for adults over 70, with a tolerable upper intake level of 100 mcg (4,000 IU) a day.⁶

For scale: the trials on this page used 20,000 IU a week, which averages roughly 2,900 IU a day — under that upper limit, but that is a description of a study protocol, not a suggestion for you. Who's actually at risk of running low, whether testing is worth it, and how much to take are all covered on our vitamin D hub, which is where that conversation belongs.

What actually moves testosterone

The unglamorous levers are the real ones: sleep, body composition, and consistent resistance training. Managing chronic stress belongs on that list too — our guide to ashwagandha for men works through the stress-and-cortisol route in detail, including how modest the honest version of that effect is.

It's also worth knowing the category's batting average before buying anything marketed as a testosterone booster. When urologists catalogued the ten commonest ingredients in top-selling "T-boosters," they found 191 studies — only 19% of them in humans at all. Among the 37 human studies, 30% (11/37) found an increase in testosterone, 46% (17/37) found no effect, 3% (1/37) found a decrease, and 22% (8/37) were indeterminate.⁷ A category whose most common result is "nothing happened" earns the skepticism this page is applying to one of its ingredients.

And the boundary that matters most: if you have persistent symptoms you're worried about, that's a conversation with a doctor and a morning blood test — not a supplement decision. Testosterone status is established by measurement and clinical judgment, and nothing on this page can tell you where you stand.

Frequently asked questions

Does vitamin D increase testosterone?

No. Randomized controlled trials have not found an effect, and the most recent meta-analysis of those trials found no clear or reproducible change in total testosterone.

Does it help if I'm vitamin D deficient?

The evidence doesn't support that either. A trial in men with low testosterone and 25(OH)D under 75 nmol/L found no effect, including in the subgroup whose vitamin D was below 50 nmol/L, and meta-analysis subgroups by baseline vitamin D status were also null. Nobody has yet run this trial in frankly deficient men.

Why do studies link low vitamin D to low testosterone?

Because both are more common in people who are heavier, older, or rarely outdoors. The two move together without one causing the other — which is why randomized trials keep coming back null.

How much vitamin D should I take for testosterone?

There's no dose that has been shown to raise testosterone. Take vitamin D for the reasons it's actually established — the recommended intake is 600 IU a day for adults up to 70 and 800 IU for adults over 70, with a 4,000 IU daily upper limit.

Is vitamin D3 better than D2 for testosterone?

Neither raises testosterone. D3 does raise blood vitamin D levels more and sustain them longer than D2, which is the reason to prefer it generally.

Should I still take vitamin D?

Possibly — just not for this. A real shortfall is worth finding and correcting, and that case stands entirely on its own.

The bottom line

Vitamin D does not raise testosterone, and the evidence saying so is better than what sits behind most supplement claims in either direction. Two randomized trials — one in men with normal testosterone, one in men with low testosterone, both measuring by mass spectrometry, both dosing 20,000 IU a week for 12 weeks — found nothing. The subgroup with the lowest vitamin D found nothing. Two meta-analyses, including subgroups by baseline vitamin D and baseline testosterone, found nothing. What's left is an observational association better explained by who tends to run low on vitamin D in the first place. Take vitamin D if you have a reason to; this isn't one. This is educational information, not medical advice.