What Vitamin D Level Is Enough?

Vitamin D is measured as serum 25-hydroxyvitamin D, and what counts as “enough” is genuinely disputed. The US and Canadian National Academies concluded in 2011 that a level of 20 ng/mL (50 nmol/L) meets the needs of nearly everyone for bone health. Other groups have argued for 30 ng/mL or more. And in 2024 the Endocrine Society stopped endorsing any target level at all, advising against routine testing in healthy adults.

This article is general information, not medical advice.

The Positions

• National Academies (Institute of Medicine), 2011. Reviewing the evidence for its Dietary Reference Intakes, the committee (Ross and colleagues) concluded that 20 ng/mL covers the needs of at least 97.5% of the population for bone health, that most people in the US and Canada reach that, and that levels above 50 ng/mL (125 nmol/L) carry potential for harm. It found the evidence for benefits beyond bone inconsistent.
• Endocrine Society, 2024. Its guideline (Demay and colleagues) recommends against routine testing of 25-hydroxyvitamin D in healthy adults under 75, and doesn’t endorse specific levels as targets, since trials haven’t identified a level that prevents disease. It suggests vitamin D supplements for some groups, such as adults over 75, pregnant people, and people with prediabetes.

What Trials Found

Large randomised trials in adults who weren’t deficient, such as the US VITAL trial of 25,871 people, found that vitamin D supplements didn’t reduce cancer or cardiovascular events. The Endocrine Society’s guideline draws on this body of trials. Benefits are clearer for people who are genuinely deficient, and for specific groups.

Units

Results come in ng/mL in the US and nmol/L in many other countries: 1 ng/mL is about 2.5 nmol/L, so 20 ng/mL is 50 nmol/L.

How Much to Take In

The Dietary Reference Intakes’ Recommended Dietary Allowance for vitamin D is 15 µg (600 IU) a day for adults to 70, and 20 µg (800 IU) over 70, with a Tolerable Upper Intake Level of 100 µg (4,000 IU) a day. Few foods contain much; oily fish, egg yolks, and fortified foods are the main sources, alongside sunlight on the skin.

Following It in Kaizora

Serum 25-Hydroxyvitamin D is a lab result on Labs, with the range your lab printed. Dietary Vitamin D comes from the foods you log, and has default reference ranges from the Dietary Reference Intakes for your sex and age, judged on the total of the 7 days ending each day: below the RDA, or above the UL. Supplements logged as foods count too.

The Short Version

• The National Academies consider 20 ng/mL (50 nmol/L) enough for bone health in nearly everyone.
• The Endocrine Society (2024) advises against routine testing in healthy adults under 75.
• Supplements didn’t prevent cancer or heart disease in trials of people who weren’t deficient.

Sources

• Ross AC et al., “The 2011 report on dietary reference intakes for calcium and vitamin D from the Institute of Medicine: what clinicians need to know,” Journal of Clinical Endocrinology & Metabolism 96, no. 1 (2011): 53–58. doi:10.1210/jc.2010-2704
• Demay MB et al., “Vitamin D for the prevention of disease: an Endocrine Society clinical practice guideline,” Journal of Clinical Endocrinology & Metabolism 109, no. 8 (2024): 1907–1947. doi:10.1210/clinem/dgae290
• Manson JE et al., “Vitamin D supplements and prevention of cancer and cardiovascular disease,” New England Journal of Medicine 380, no. 1 (2019): 33–44. doi:10.1056/NEJMoa1809944