What Is Vitamin D (25-OH)?
What it is
25-hydroxyvitamin D is the main circulating form of vitamin D, reflecting body stores.
Why it matters
Used to screen for vitamin D deficiency.
Specimen
Whole blood / serum / plasma
Interpretation
Low = vitamin D deficiency/insufficiency.
Limitations
Screening aid; confirm borderline results quantitatively.
Related test: Vitamin D Rapid Test — specimen: WB
Frequently Asked Questions
What does low vitamin D mean? Deficiency or insufficiency; confirm borderline results quantitatively.
References
- Clinical guidance on vitamin D testing.
Last reviewed: 2026-09-12