Identify the measurement
25-hydroxyvitamin D is the measurement commonly used when assessing vitamin D status. It should not be confused with 1,25-dihydroxyvitamin D, which has different uses. Preserve the analyte name and units before comparing values from articles, products or laboratory reports. [1]
Use the current laboratory interval
Quest lists 30–100 ng/mL for its named immunoassay. Labcorp's assay page, updated in September 2026, lists 20.0–100.0 ng/mL. This difference is a practical reason to cite the exact assay and review date instead of copying an undated normal-range graphic. [2] [3]
Read target claims against current guidance
The 2024 Endocrine Society guideline does not establish outcome-specific target concentrations for generally healthy adults. A laboratory's upper reference limit should not be interpreted as a concentration everyone should try to reach. Risk, clinical context and the reason for testing remain relevant. [4]
Keep trends comparable
Record the assay, units, relevant supplement use and testing context with each result. Comparable measurements are more useful than an isolated target copied from a different source. Discuss the interpretation of an unexpected result with a clinician rather than using the upper edge of a range as a general goal. [1] [4]
| Marker | Quest example | Labcorp example |
|---|---|---|
| 25-OH vitamin D | 30–100 ng/mL. Assay source ↗ | 20.0–100.0 ng/mL; updated September 2026. Assay source ↗ |
These notes explain sources and testing context. They do not diagnose a condition, select a personal supplement dose or replace professional medical advice.