Vitamin D, 25-OH
Vitamin D, 25-OH, is the main form used to assess the body’s vitamin D. It depends on sunlight, so it is usually lower in winter.
At a glance
- Sample
- Blood
- Units
- ng/mL (US), nmol/L (Europe)
- Often looked at with
- Vitamin B12, Folate
- Preparation
- No special preparation is usually needed. If other tests are done from the same sample, you may be asked to come fasting.
Units: ng/mL and nmol/L
US labs usually print vitamin D, 25-OH in ng/mL, most European labs in nmol/L. To convert, multiply ng/mL by 2.496.
nmol/L = ng/mL × 2.496 · molar mass 400.64 g/mol
This converter changes units only. It doesn’t tell you whether a number is in or out of any range: that depends on the range printed by your own lab, and on your doctor. Soma does not diagnose and is not medical advice.
Why lab ranges differ
Each lab sets its reference range for its own method and analyser, and many ranges differ by age and sex. Two labs can print different ranges for the same blood, so a result is read against the range on its own report, not against a number from another lab or a website.
Soma charts every vitamin D, 25-OH result against the range printed by the lab that measured it.
What can affect the result
- Season: higher at the end of summer, lower at the end of winter.
- Different lab methods give different numbers.
- Recently started supplements: the level settles over months.
If something like this applies, mention it to the doctor who reads your results.
Questions
How do I convert vitamin D, 25-OH from ng/mL to nmol/L?
Multiply ng/mL by 2.496. For example, 30 ng/mL is 74.9 nmol/L.
Why does my lab’s vitamin D, 25-OH range differ from another lab’s?
Each lab sets its range for its own method and equipment, and many ranges differ by age and sex. That’s why a result is best read against the range printed on the same report.
How do I prepare for a vitamin D, 25-OH test?
No special preparation is usually needed. If other tests are done from the same sample, you may be asked to come fasting. Follow your lab’s instructions.
Related tests
Got a lab report with Vitamin D, 25-OH?
Share it to Soma: it reads every row on your phone, with no account and no upload, and puts your vitamin D, 25-OH on one chart with your earlier results, each against the range your lab printed.
Sources
- Vitamin D Test — MedlinePlus, U.S. National Library of Medicine.
- Units: PubChem: Calcifediol (calcifediol, 25-hydroxyvitamin D₃), molar mass 400.64 g/mol, as the Soma app converts.
Mention of a source doesn’t mean it endorses Soma. This page explains the test; it doesn’t diagnose and is not medical advice. Talk to your doctor about what your results mean.