Vitamins & minerals
Vitamin D
LOINC 1989-3 · ng/mL
Ranges
Reference range: 30–100 ng/mL
What it is
Vitamin D helps your body absorb calcium and supports bones, muscles and the immune system. Your skin makes it from sunlight.
Why it matters
It is one of the most common deficiencies and matters for bone strength, muscle function and immunity.
What high values can mean
A higher value usually comes from supplements; very high levels can be harmful and are interpreted by a clinician.
What low values can mean
A lower value is common, especially with limited sun, and can affect bones and muscles.
How to improve it
Sensible sun exposure, vitamin-D-rich or fortified foods, and supplements when advised raise low levels.
Food & lifestyle
Oily fish, egg yolks and fortified foods provide some vitamin D; many people need a supplement, especially in winter.
Preparing for the test
A blood test; fasting is not required — follow your lab's instructions.
When to talk to a doctor
Discuss a low vitamin D with a doctor to choose the right supplement dose for you.
Related markers
Sources
- NIH Office of Dietary Supplements
- MedlinePlus (NIH)
Content reviewed on June 26, 2026
Medical disclaimer
This content is for educational purposes only. It is not medical advice and does not diagnose, treat, or prevent any condition. Reference ranges vary between laboratories — always use the range printed on your report and discuss your results with a healthcare professional.
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