---
title: "Fasting Serum Insulin Optimal Range vs Lab Normal (2026 Clinical Decoder & Protocol) | Nutrition Research Labs"
source_url: "https://nutritionresearchlabs.com/biomarkers/fasting-insulin"
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description: "Decode your Fasting Serum Insulin (Fasting Insulin) blood test: Longevity Optimal Target (2.0–5.5 uIU/mL) vs Standard Lab Normal (2.6–24.9 uIU/mL), assay interference, and Grade-A clinical protocols."
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> **Canonical Source:** [https://nutritionresearchlabs.com/biomarkers/fasting-insulin](https://nutritionresearchlabs.com/biomarkers/fasting-insulin)
>
> *Decode your Fasting Serum Insulin (Fasting Insulin) blood test: Longevity Optimal Target (2.0–5.5 uIU/mL) vs Standard Lab Normal (2.6–24.9 uIU/mL), assay interference, and Grade-A clinical protocols.*

## Reference Range Comparison (uIU/mL)

- **Longevity & Metabolic Optimal Range:** 2.0 – 5.5 uIU/mL
- **Standard Lab Reference Interval ("Normal"):** 2.6 – 24.9 uIU/mL
- **Why Standard Lab Ranges Mislead Patients:** The typical reference range of 2.6 to 24.9 uIU/mL captures an unhealthy cross-section of the population. An individual with a fasting insulin of 18 uIU/mL will be reported as entirely
- **Pre-Draw Supplement Assay Interference Warning:** Endogenous anti-insulin antibodies or human anti-mouse antibodies (HAMA) cause significant assay interference in standard double-antibody radioimmunoassays and electrochemiluminescent assays.

## Decode the Next Biomarker on Your Blood Panel

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