Vitamin D Converter (ng/mL to nmol/L)
Convert a 25-hydroxyvitamin D blood level between ng/mL and nmol/L (1 ng/mL = 2.496 nmol/L) and see the deficiency, insufficiency and sufficiency bands used by the Endocrine Society and the IOM.
How it works
nmol/L = ng/mL × 2.496 · ng/mL = nmol/L ÷ 2.496 (≈ 0.4) (25-hydroxyvitamin D₃ molar mass 400.6 g/mol)
Blood vitamin D status is measured as 25-hydroxyvitamin D. US laboratories usually report it in ng/mL and most others in nmol/L; because 25(OH)D weighs about 400.6 g/mol, 1 ng/mL equals 2.496 nmol/L (often rounded to 2.5). Two sets of cut-offs are widely quoted: the Endocrine Society’s 2011 guideline (deficiency below 20 ng/mL, insufficiency 21–29, sufficiency 30–100) and the Institute of Medicine / National Academy of Medicine report (20 ng/mL or more is adequate for bone health in almost everyone, above 50 ng/mL may be harmful). The Endocrine Society’s 2024 guideline no longer recommends routine testing or fixed targets for healthy people.
Worked example
A level of 30 ng/mL × 2.496 = 74.9 nmol/L. That is “sufficient” on the Endocrine Society 2011 scale (30–100 ng/mL) and “adequate for bone health” on the IOM scale (20–50 ng/mL).
Sources: Holick MF et al. Evaluation, treatment and prevention of vitamin D deficiency: Endocrine Society guideline. J Clin Endocrinol Metab 2011;96:1911–30 · NIH Office of Dietary Supplements: Vitamin D fact sheet for health professionals
Frequently asked questions
How do I convert vitamin D from nmol/L to ng/mL?
Divide by 2.496 (or multiply by 0.4 for a quick estimate). For example 50 nmol/L = 20.0 ng/mL and 75 nmol/L = 30.0 ng/mL.
What vitamin D level is deficient?
Below 20 ng/mL (50 nmol/L) is called deficiency by the Endocrine Society, and below 12 ng/mL (30 nmol/L) puts people at risk of deficiency according to the IOM. Severe deficiency, below about 10 ng/mL (25 nmol/L), can cause rickets or osteomalacia.
What vitamin D level is too high?
Toxicity is rare and usually appears only above about 150 ng/mL (375 nmol/L) with high-dose supplements. The IOM notes possible harm above 50 ng/mL (125 nmol/L), and the Endocrine Society 2011 guideline set 100 ng/mL (250 nmol/L) as the upper safe limit.
Is 25(OH)D the right vitamin D test?
Yes. 25-hydroxyvitamin D reflects intake and sun exposure over weeks and is the standard test for status. The active form, 1,25-dihydroxyvitamin D, is used only in special situations such as kidney disease or calcium disorders.
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Educational calculation only, not medical advice or a diagnosis. Reference ranges and units differ between laboratories; interpret any result with your doctor in the context of your full clinical picture.