Fasting Insulin
Fasting insulin measures the amount of insulin your pancreas produces in a fasted state. Insulin is the hormone responsible for shuttling glucose from the blood into cells. When cells become resistant to insulin's signal, the pancreas compensates by producing more insulin — a state called hyperinsulinemia.
Elevated fasting insulin is one of the earliest detectable signs of metabolic dysfunction, often appearing years before fasting glucose or HbA1c become abnormal. By the time glucose is elevated, insulin resistance is typically well-established.
Fasting insulin is used alongside fasting glucose to calculate HOMA-IR (Homeostatic Model Assessment of Insulin Resistance), one of the most validated markers of insulin sensitivity. Many longevity-focused practitioners consider fasting insulin one of the most important biomarkers for metabolic health optimization.
What It Measures
Fasting insulin measures the baseline insulin output from the pancreas after 10–12 hours without food. It reflects how hard your body is working to maintain normal blood sugar levels.
Reference Ranges
| Status | Range (uIU/mL) |
|---|---|
| Optimal | 2–5 uIU/mL |
| Normal | 5–10 uIU/mL |
| Borderline | 10–15 uIU/mL |
| Out of Range | > 15 uIU/mL |
Optimal Ranges
| Group | Range | Unit | Source |
|---|---|---|---|
| Standard | 2.6–24.9 | uIU/mL | Standard reference |
| Optimal (functional) | 3–8 | uIU/mL | Functional range |
When Values Are High
Elevated fasting insulin is one of the earliest markers of insulin resistance — often years before blood sugar rises. Associated with weight gain, PCOS, cardiovascular risk, and cancer risk.
When Values Are Low
Low fasting insulin (<2 uIU/mL) may indicate type 1 diabetes, pancreatic insufficiency, or prolonged fasting. In the context of normal glucose, low insulin reflects excellent insulin sensitivity.
What To Do
Lifestyle
- •Resistance training is the most effective insulin sensitizer
- •Walk after meals to improve glucose disposal
- •Time-restricted eating (12–16 hour window) reduces fasting insulin
- •Prioritize sleep — even one night of poor sleep impairs insulin sensitivity
Supplements
- •Berberine 500mg 2x/day has significant insulin-sensitizing effects
- •Chromium picolinate (200–1000mcg)
- •Magnesium glycinate if deficient
When to Retest
Retest 8–12 weeks after lifestyle changes (must fast 12+ hours)
How GATOR Tracks This
Lab Providers
Related Clinical Ratios
Related Biomarkers
This content is for informational purposes only and does not constitute medical advice. Reference ranges may vary by laboratory and individual factors. Consult a qualified healthcare provider for interpretation of your results and treatment decisions.
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