lab metric
25(OH)D
Table of contents
Description
25‑hydroxyvitamin D (25(OH)D) is the main blood marker used to assess vitamin D status. Vitamin D supports bone mineralization, muscle function, and aspects of immune regulation. Because levels depend on sun exposure, season, geography, skin pigmentation, body fat, and supplementation, it’s a useful “status check” rather than a diagnosis by itself.
Why it matters
Low vitamin D is associated with higher risk of low bone density and fractures, and it can contribute to muscle weakness in severe cases. It’s commonly monitored in people with limited sun exposure, malabsorption, obesity, or chronic kidney disease.
Interpreting results (general)
Cutoffs vary by guideline, but many clinicians consider:
< 20 ng/mL: deficiency
20–30 ng/mL: insufficiency
30–50 ng/mL: commonly targeted “adequate” range
Very high levels can occur with excessive supplementation and may raise hypercalcemia risk.
Practical notes
Vitamin D is best interpreted with calcium (and sometimes PTH) when abnormalities are present. If supplementing, retesting after a consistent period helps confirm response.
Educational only, not medical advice. Supplement dosing and targets should be individualized with a clinician, especially with kidney disease, history of kidney stones, or hypercalcemia.
Frequently Asked Questions
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