In brief
Measures 25-hydroxyvitamin D, the form of vitamin D made in the liver, which shows your overall vitamin D level.
What it measures
25-hydroxyvitamin D (25(OH)D), reported in nmol/L.
Why it is done
To check vitamin D levels, especially in people with limited sun exposure or naturally dark skin.
Reading the results
- Less than 12.5 nmol/L: severely deficient.
- 12.5 to 29 nmol/L: moderately deficient.
- 30 to 49 nmol/L: mildly deficient.
- 50 to 200 nmol/L: sufficient for bone health.
Reference ranges
| Result | Range |
|---|---|
| Severely deficient | Less than 12.5 nmol/L |
| Moderate deficiency | 12.5 to 29 nmol/L |
| Mildly deficient | 30 to 49 nmol/L |
| Sufficient for bone health | 50 to 200 nmol/L |
Ranges differ between laboratories. Always compare a result with the range printed on your own report, and ask your doctor what it means for you.
Before the test
None.
Units. nmol/L in Australia. Convert US ng/mL results with the lab units tool.
What can affect the result
- Season: levels are higher at the end of summer and lower over winter
- Some seizure medicines, particularly phenytoin
- Vitamins and supplements
Related topics
Connections
Vitamin D test measures
The test measures 25(OH)D, the form of vitamin D made in the liver.
Sources
Test information summarised from the sources listed on this page, read on 19 October 2026. General education only, not medical advice. Spotted a mistake? Please tell us through the HuBu-Intel contact page.