Fasting Glucose
Fasting glucose measures the concentration of glucose in the blood after 10–12 hours of fasting. It is one of the most commonly ordered lab tests and serves as a primary screening tool for diabetes and prediabetes.
While fasting glucose is useful, it's important to understand that it's a relatively late marker of metabolic dysfunction. Fasting insulin often rises years before fasting glucose becomes abnormal, as the pancreas compensates by producing more insulin. By the time fasting glucose is elevated, significant insulin resistance has usually developed.
For optimal metabolic health monitoring, fasting glucose should be interpreted alongside fasting insulin (to calculate HOMA-IR) and HbA1c (for a longer-term average). The combination of all three provides the most complete picture of glycemic control and insulin sensitivity.
What It Measures
Fasting glucose measures the amount of glucose (sugar) in the blood after an overnight fast. It reflects the liver's glucose output and the body's ability to regulate blood sugar in a fasted state.
Reference Ranges
| Status | Range (mg/dL) |
|---|---|
| Optimal | 70–85 mg/dL |
| Normal | 70–99 mg/dL |
| Borderline | 100–125 mg/dL (prediabetes) |
| Out of Range | >= 126 mg/dL (diabetes) |
Optimal Ranges
| Group | Range | Unit | Source |
|---|---|---|---|
| Normal | 70–99 | mg/dL | ADA guidelines |
| Prediabetes | 100–125 | mg/dL | ADA guidelines |
| Optimal | 72–90 | mg/dL | Functional range |
When Values Are High
Elevated fasting glucose indicates impaired glucose regulation. 100–125 mg/dL is prediabetes; ≥126 mg/dL on two occasions is diabetes. Fasting insulin may be elevated years before glucose rises.
When Values Are Low
Fasting glucose <70 mg/dL is hypoglycemia. Causes include excess insulin, prolonged fasting, alcohol, or liver disease. Symptoms: shakiness, confusion, sweating.
What To Do
Lifestyle
- •Resistance training improves glucose disposal
- •Post-meal walks (10–15 min) reduce glucose spikes
- •Fiber-first eating order: vegetables → protein → carbs
- •Consistent meal timing and sleep schedule
Supplements
- •Berberine 500mg before meals
- •Chromium picolinate 200–1000mcg
- •Ceylon cinnamon (1–3g/day) may modestly improve glucose
When to Retest
Retest with HbA1c and fasting insulin for complete picture
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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