Vitamin D (25-Hydroxy): Normal Range, High & Low Causes
What Vitamin D measures
The 25-hydroxy vitamin D test shows how much vitamin D your body has from sunlight, food and supplements. Vitamin D helps your body absorb calcium for bones and supports muscles.
Vitamin D reference ranges
| Category | Conventional units | SI units |
|---|---|---|
| Deficient | Below 12 ng/mL | Below 30 nmol/L |
| Inadequate for some people | 12 – 19 ng/mL | 30 – 49 nmol/L |
| Adequate for most people | 20 – 50 ng/mL | 50 – 125 nmol/L |
| Possible harm at the high end | Above 50 ng/mL | Above 125 nmol/L |
Guideline bodies disagree: the Endocrine Society treats levels below 20 ng/mL as deficiency and 21–29 ng/mL as insufficiency. Use your clinician’s target.
Need to convert units? Use the ng/mL ↔ nmol/L converter.
Common causes of a high result
- Taking very high-dose supplements
- Rarely, granulomatous diseases or some lymphomas
Common causes of a low result
- Little sun exposure, covered clothing or darker skin at higher latitudes
- Low dietary intake
- Obesity
- Malabsorption (celiac disease, Crohn’s disease, gastric surgery)
- Kidney or liver disease
- Some medicines, including certain anticonvulsants
How to prepare for the test
No fasting needed. Mention any vitamin D or multivitamin you take.
How often to retest
About 3 months after starting or changing supplements, then as advised.
Track Vitamin D over time
Upload your reports and Labgist plots every Vitamin D result on one timeline, converts units and shows what changed.
Get the appFrequently asked questions
What is a normal vitamin D level?
Most guidance treats 20 ng/mL (50 nmol/L) or above as adequate, below 12 ng/mL as deficient, and some groups prefer 30 ng/mL or more.
Is vitamin D deficiency common?
Yes, in many parts of the world, including sunny countries, because of indoor lifestyles, clothing, skin tone and diet.
Can you take too much vitamin D?
Yes. Very high doses can raise blood calcium and cause nausea, kidney problems and other harm, so use the dose your clinician recommends.
Related tests
Sources
This page is general education and was last updated 2026-10-30. It is not a substitute for medical advice. See our editorial approach.