What does my vitamin D level mean?
Convert your lab result between ng/mL and nmol/L
Medical Disclaimer: This tool provides general educational estimates. Always consult your prescribing physician or healthcare provider before making medication changes or interpreting results from population-based models.
Frequently Asked Questions
The conversion factor is 2.496 (often rounded to 2.5). To convert ng/mL to nmol/L, multiply by 2.496. To convert nmol/L to ng/mL, divide by 2.496 (or multiply by 0.4).
Most US labs report vitamin D in ng/mL, while laboratories in Europe, Canada, and Australia typically use nmol/L. The unit should be listed on your lab report next to your 25(OH)D result.
Vitamin D levels below 20 ng/mL (50 nmol/L) are considered deficient. Levels of 20-29 ng/mL (50-72 nmol/L) are insufficient. Levels of 30-100 ng/mL (75-250 nmol/L) are sufficient. Above 100 ng/mL (250 nmol/L) is potentially toxic.
The US uses weight-based measurement (ng/mL), while most other countries adopted the International System of Units (SI), which uses substance concentration (nmol/L). Both measure the same thing — your blood level of 25-hydroxyvitamin D.
Vitamin D testing measures 25-hydroxyvitamin D [25(OH)D] in your blood, which is the primary circulating form and the best indicator of your vitamin D status. The test requires a simple blood draw and can be ordered by your healthcare provider.
Sources
- Holick MF, Binkley NC, et al. Evaluation, treatment, and prevention of vitamin D deficiency: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2011;96(7):1911-1930. Link
- Demay MB, Pittas AG, et al. Vitamin D for the prevention of disease: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2024;109(8):1907-1947. Link
- Institute of Medicine. Dietary Reference Intakes for Calcium and Vitamin D. Washington, DC: National Academies Press; 2011. Link
- National Institutes of Health Office of Dietary Supplements. Vitamin D — Health Professional Fact Sheet. Link
- Cashman KD, Dowling KG, Skrabakova Z, et al. Vitamin D deficiency in Europe: pandemic? Am J Clin Nutr. 2016;103(4):1033-1044. Link
Methodology
This calculator converts between the two standard units used to report serum 25-hydroxyvitamin D [25(OH)D] levels: ng/mL (conventional units used primarily in the United States) and nmol/L (SI units used internationally).
nmol/L = ng/mL × 2.496
The conversion factor of 2.496 is derived from the molecular weight of 25-hydroxyvitamin D (calcidiol) at 400.65 g/mol. Reference ranges are based on the Endocrine Society 2011 clinical practice guideline and the 2024 update.
To convert vitamin D levels: multiply ng/mL by 2.496 to get nmol/L, or divide nmol/L by 2.496 to get ng/mL. US labs typically report in ng/mL, while UK, European, and Australian labs use nmol/L. A level below 20 ng/mL (50 nmol/L) is considered deficient. Levels of 20-29 ng/mL (50-72 nmol/L) are insufficient. The sufficient range is 30-100 ng/mL (75-250 nmol/L). Above 100 ng/mL (250 nmol/L) is potentially toxic.
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