Biomarker guide
Fasting Glucose (mg/dL)
Fasting glucose measures the amount of sugar circulating in your blood after at least eight hours without food. It is one of the most widely used markers of blood-sugar regulation, and people test it to track metabolic health over time and to see where they fall relative to commonly used reference ranges.
Reference ranges
Commonly used adult reference ranges. Labs vary in methodology and cutoffs, interpret your results against your lab report's stated ranges and with your doctor.
Commonly used reference ranges place fasting glucose at 70–99 mg/dL; results vary with sleep, stress, and recent illness, and labs differ slightly.
| Zone | Range |
|---|---|
| Low | 50–70 mg/dL |
| Optimal | 70–100 mg/dL |
| Prediabetic range | 100–126 mg/dL |
| Diabetic range | 126–160 mg/dL |
The importance of Fasting Glucose
Glucose is the body’s primary fuel, and the fasting value shows how well insulin keeps blood sugar in a steady band when no food is coming in. A single reading is a snapshot; the trend across several tests is far more informative than any one number.
Values that drift upward year over year, even within the normal range, are associated with declining insulin sensitivity. Sleep, stress, illness, certain medications, and even a hard workout the day before can all nudge a fasting reading, which is why labs and clinicians look at patterns rather than one-off results.
If your fasting glucose sits in the 100–125 mg/dL range on repeat tests, that pattern is worth discussing with your doctor, often alongside HbA1c and fasting insulin, which together give a fuller picture of glucose regulation.
Frequently asked questions
What is a normal fasting glucose level?
For most adults, commonly used reference ranges place fasting glucose between 70 and 99 mg/dL. Readings of 100–125 mg/dL fall in what many labs label the prediabetic range, and 126 mg/dL or higher falls in the diabetic range. Individual labs vary slightly, so compare your result against the range printed on your own report.
Why do I need to fast before a glucose test?
Fasting for at least eight hours removes the effect of recent meals, so the test reflects your baseline blood-sugar regulation rather than what you last ate. Water is fine during the fast; food, sugary drinks, and even some supplements can raise the reading.
Can fasting glucose be high without diabetes?
Yes. Poor sleep, acute stress, illness, certain medications such as steroids, and the natural early-morning rise in cortisol can all elevate a single fasting reading. That is why clinicians look at repeat results and companion markers like HbA1c before drawing conclusions, and why an unexpected result is worth discussing with your doctor.
How often should I test fasting glucose?
Many people include fasting glucose in an annual lab panel, while those tracking a rising trend or making lifestyle changes often retest every three to six months. Your doctor can help you pick a cadence that fits your history and goals.
Panels that measure Fasting Glucose
Diabetes Blood Test Panels: HbA1c, Glucose & Insulin Monitoring
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View panelDiabetes Blood Test Panels: A1c, Glucose & Insulin Monitoring
Eight tiered lab panels that look beyond blood sugar, tracking glucose control alongside kidney, lipid, insulin, and inflammation markers.
View panelComprehensive Blood Test Panel: 17 Tests, 78 Biomarkers
One blood draw, 78 biomarkers, walk into your next appointment with real data.
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