Indicator Explainer
25-OH Vitamin D
The main circulating vitamin D metabolite — the standard measure of vitamin D status.
This page explains what the indicator is and how results are interpreted in general terms. Reference ranges depend on the laboratory, the method, and your own situation — no single “normal value” applies to everyone. This page is health information, not a diagnosis. For symptoms, treatment, or urgent concerns, contact a healthcare professional.
When it is tested
Measured in bone-health assessments, in malabsorption and chronic kidney disease follow-up, and before and during high-dose supplementation.
Reading results
Values depend on season, latitude, skin tone, body weight, and supplementation timing, and fluctuate across the year. Assays differ measurably — immunoassay and LC-MS/MS results are not interchangeable — so serial monitoring should stay on one method and one laboratory. What counts as deficient versus insufficient varies between guidelines and remains actively debated.
Questions to ask a professional
- Which assay and laboratory was used — will monitoring stay on the same method?
- What season and supplementation pattern applies to this value?
- Which guideline’s thresholds is this report using?