Vitamin D (25-OH)
25-OH Vitamin D
- Sample
- Blood
- Usual units
- ng/mL
Also known as 25-OH Vitamin D · 25 Hydroxy Vitamin D · 25-Hydroxyvitamin D · Vitamin D Total · Vit D · 25(OH)D
What this test measures
The 25-hydroxy vitamin D test measures the main storage form of vitamin D circulating in blood. It is the form the liver produces after vitamin D is made in skin or absorbed from food. Vitamin D participates in calcium and phosphorus handling in the body. A lab measures this particular form because it is more stable in blood than the active hormone form, giving a fuller picture of vitamin D status. The result is usually reported in nanograms per milliliter (ng/mL).
Reading your report
There isn’t one standard range for this test — each lab prints its own. Use the range shown next to your result.
Vitamin D (25-OH) unit converter
Convert Vitamin D (25-OH) units
Labs print this test in ng/mL or nmol/L depending on where the sample was run.
Related guides
- Guide
Why the same blood test has different "normal" ranges at different labs
Reference intervals are built from each lab's own population and equipment, which is why two labs can print different ranges for the same sample.
- Guide
Reference interval, cutoff, and the "optimal" numbers online: three different things
The range beside your result, the target a website quotes, and the threshold that defines a condition are built in different ways and answer different questions.
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Why the same lab printed a different reference range for you this year
Ranges are not fixed constants. The lab can change method, revise its reference group, or apply a range that depends on your age — none of which is an error.
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Panels, profiles and packages: what you actually paid for
A panel is a bundle of individual tests sold under one name, and the names are not standardised. How to work out what a package included — and what it left out.