Is my Fasting Glucose normal?
Free blood test checker · Standard + longevity-optimal ranges
What is a normal Glucose level?
Fasting glucose measures blood sugar after 8+ hours of fasting. It's a key marker for diabetes risk. Normal is 65-100 mg/dL, prediabetes is 100-125 mg/dL, and diabetes is 126+ mg/dL. Longevity-optimal is 65-90 mg/dL.
| Range | Values |
|---|---|
| Standard Reference | 65–100 mg/dL |
| Optimal | 65–90 mg/dL |
| Longevity Optimal | 65-90 mg/dL |
| High Risk | > 126 mg/dL |
What causes abnormal Glucose levels?
Elevated fasting glucose is caused by insulin resistance (the body's cells don't respond well to insulin), excess refined carbohydrate and sugar intake, sedentary lifestyle, obesity, chronic stress (cortisol raises blood sugar), poor sleep, certain medications (corticosteroids, beta-blockers), and genetic predisposition to type 2 diabetes. Note: very low fasting glucose (<70 mg/dL) can indicate hypoglycemia, causing dizziness, shakiness, or confusion — especially important if you take diabetes medication.
When should you see a doctor?
See your doctor if fasting glucose is above 100 mg/dL (prediabetes) or above 126 mg/dL (diabetes threshold). Also consult if you have symptoms like increased thirst, frequent urination, blurred vision, or unexplained weight loss. Your doctor will likely order an HbA1c test for confirmation.
Glucose and longevity
Fasting glucose is a lagging indicator — by the time it rises above 100 mg/dL, insulin resistance has likely been present for years. Fasting insulin and HOMA-IR catch metabolic dysfunction 5-10 years earlier. The longevity-optimal glucose range of 65-90 mg/dL reflects the metabolic flexibility seen in centenarian populations, where tight glycemic control correlates with preserved cognitive function and reduced cardiovascular events. Post-meal glucose spikes (which fasting glucose does not capture) may be equally important — continuous glucose monitors (CGMs) reveal that many people with "normal" fasting glucose have significant postprandial excursions above 140 mg/dL.
Where to get a Glucose test
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Related biomarkers
These biomarkers are often tested alongside Glucose for a more complete picture.
Related calculators
Composite scores that use Glucose as an input.
Frequently asked questions
What is a normal fasting glucose level?
Why is my fasting glucose high?
How do I lower fasting glucose?
What is the functional medicine optimal glucose range?
Why is fasting insulin more important than fasting glucose?
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Sources: Reference ranges based on AHA/ACC, ADA, and AACE clinical guidelines. Biological variation data from Ricos/Westgard database. Longevity-optimal ranges reflect targets used by preventive and functional medicine practitioners.
Last reviewed: April 2026. This tool provides general health information and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult your healthcare provider about your specific results.