---
title: "25-Hydroxy Vitamin D [25(OH)D Calcifediol] Optimal Range vs Lab Normal (2026 Clinical Decoder & Protocol) | Nutrition Research Labs"
source_url: "https://nutritionresearchlabs.com/biomarkers/vitamin-d-25-oh"
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description: "Decode your 25-Hydroxy Vitamin D [25(OH)D Calcifediol] (Vitamin D3) blood test: Longevity Optimal Target (45–65 ng/mL) vs Standard Lab Normal (30–100 ng/mL), assay interference, and Grade-A clinical protocols."
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---

> **Canonical Source:** [https://nutritionresearchlabs.com/biomarkers/vitamin-d-25-oh](https://nutritionresearchlabs.com/biomarkers/vitamin-d-25-oh)
>
> *Decode your 25-Hydroxy Vitamin D [25(OH)D Calcifediol] (Vitamin D3) blood test: Longevity Optimal Target (45–65 ng/mL) vs Standard Lab Normal (30–100 ng/mL), assay interference, and Grade-A clinical protocols.*

## Reference Range Comparison (ng/mL)

- **Longevity & Metabolic Optimal Range:** 45 – 65 ng/mL
- **Standard Lab Reference Interval ("Normal"):** 30 – 100 ng/mL
- **Why Standard Lab Ranges Mislead Patients:** Labs label 30 ng/mL as
- **Pre-Draw Supplement Assay Interference Warning:** Liquid chromatography-tandem mass spectrometry (LC-MS/MS) is the gold standard. Chemiluminescent immunoassays frequently fail to differentiate 25(OH)D2 from 25(OH)D3 or cross-react with C3-epimer metabolites.

## Decode the Next Biomarker on Your Blood Panel

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