What does the vitamin D blood test measure?
It measures 25-hydroxyvitamin D, often written 25(OH)D, the form your liver makes from the vitamin D you get from sunlight, food and supplements. MedlinePlus explains that this is the test used to check whether you have enough. A different test, 1,25-dihydroxyvitamin D, measures the active hormone and is used mainly for kidney problems or abnormal calcium, not for checking your stores.
Results are reported in ng/mL in the United States or nmol/L elsewhere; 20 ng/mL equals 50 nmol/L. As with any test, reference ranges and the cutoffs labs flag can differ, so read the units on your report before comparing it with anything online.
What do the 20 and 30 ng/mL cutoffs mean?
They come from two different ways of answering “how much is enough.” The Institute of Medicine, in a 2011 report summarized for clinicians, concluded that a 25(OH)D level of at least 20 ng/mL meets the needs of at least 97.5 percent of the population for bone health. The same committee found that higher levels were not consistently linked to more benefit and that the prevalence of vitamin D inadequacy in North America had been overestimated.
Others aim higher. The MedlinePlus encyclopedia notes that many experts recommend a level of 30 to 80 ng/mL (75 to 200 nmol/L).
| 25(OH)D level | How it is usually read |
|---|---|
| Under 20 ng/mL | Below the IOM’s bone-health threshold |
| 20 to 29 ng/mL | Enough for bone health by the IOM standard; below the higher target some experts use |
| 30 ng/mL and above | Meets the higher target many labs and experts use |
The newest guidance pulls back on testing altogether. The Endocrine Society’s 2024 guideline, which replaced its 2011 version, suggests against routine 25(OH)D testing in generally healthy adults under 75, because levels that give outcome-specific benefits have not been established in trials. Testing still makes sense when there is a reason, such as bone loss, malabsorption or low calcium.
What do trials show about vitamin D and testosterone?
They show no reliable boost in healthy men. An early trial followed 54 overweight men in a weight-loss program who started out low in vitamin D. In the 31 who took about 3,332 IU daily for a year, total testosterone rose from 10.7 to 13.4 nmol/L, while the 23 on placebo saw no change. The authors called for larger trials to test the idea.
A larger trial, by a team that included the earlier study’s lead author, did not confirm it. In a randomized controlled trial of 100 healthy men with low testosterone and 25(OH)D under 75 nmol/L, 20,000 IU of vitamin D3 a week for 12 weeks had no significant effect on total testosterone measured by mass spectrometry, or on free testosterone, SHBG, LH or FSH. The conclusion was direct: vitamin D had no effect on testosterone in middle-aged healthy men with low levels.
The practical reading is that correcting a real deficiency is worth doing for bone and general health, but vitamin D is not a testosterone treatment. Our page on whether testosterone boosters work applies the same test to other supplements, and the total testosterone blood test page explains how low testosterone is actually confirmed.
What raises or lowers your vitamin D level?
Sun, food and supplements raise it; little sun and poor absorption lower it. MedlinePlus notes that your skin makes vitamin D when bare skin is exposed to sunlight without sunscreen, that only a few foods supply it, and that people with conditions that impair absorption, such as Crohn disease, ulcerative colitis or celiac disease, are at higher risk of low levels. Southern California sunshine does not ensure a good level if you work indoors; our article on vitamin D deficiency in Los Angeles men looks at why.
Low vitamin D matters most for bones. If you have had a low-trauma fracture or a low bone density scan, our page on low bone density in men explains the wider workup.
How Ultimate Male checks vitamin D
Vitamin D is on our Targeted Preventative Health Panel and on the published marker list for our comprehensive panel, drawn same day at San Gabriel or Downey with results in 24 to 48 hours. The nutrient deficiency panel page covers the nutrient side of our testing.
If your level is low, a PA-C or MD explains what it means for you and whether supplementation makes sense, and sets any dose; our page on vitamin D3 for men with low levels describes the options. If you came in hoping vitamin D would fix low energy or low testosterone, you will get a straight answer about what the evidence supports. All panels are listed on the preventative blood testing page.
