Fasting Glucose: normal range and what it means
Short answer: The normal fasting glucose range is 70 – 100 mg/dL for adults. Within that, 70 – 90 mg/dL is optimal. In SI units that is about 3.9 – 5.5 mmol/L. Labs differ a little, so also check the range printed on your report.
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Information, not a diagnosis. Talk to a doctor about your result, and sooner if you feel unwell.
Blood sugar after an overnight fast — a core metabolic-health signal.
Normal range
Adult reference range.
- Low< 70 mg/dL
- Optimal70 – 90 mg/dL
- Normal90 – 100 mg/dL
- Pre-diabetic100 – 126 mg/dL
- High≥ 126 mg/dL
What it measures
The amount of sugar in your blood after not eating for 8+ hours. It reflects how well your body keeps glucose in check at rest.
What moves it
Diet (especially refined carbs), stress, sleep, physical activity, and insulin sensitivity.
How to bring it into range
Regular movement, strength training, fibre, limiting refined carbs, and consistent sleep all lower fasting glucose.
How fast it responds
Day-to-day with lifestyle; meaningful trend shifts over weeks.
Also reported as: glucose fasting · fbs · blood sugar fasting
Fasting Glucose is one of nine markers in biological ageThe free PhenoAge calculator turns it and eight other routine results into your phenotypic age.See where your own value lands
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Common questions
- What is the normal fasting glucose range?
- The normal fasting glucose range is 70 – 100 mg/dL for adults. Within that, 70 – 90 mg/dL is optimal. In SI units that is about 3.9 – 5.5 mmol/L. Labs differ a little, so also check the range printed on your report.
- What does a high Fasting Glucose mean?
- A value above the reference band means Fasting Glucose is outside the range typical for a healthy adult. A single reading is rarely conclusive on its own — what matters is the trend across draws and the other markers around it, which is why HealthOS reads the whole panel together rather than one number at a time.
- How do I improve my Fasting Glucose?
- Regular movement, strength training, fibre, limiting refined carbs, and consistent sleep all lower fasting glucose.
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Reference ranges are general-population guidance compiled from common clinical laboratories, not a diagnosis. Lab-to-lab ranges differ. Always read your results with your doctor.