Fasting Glucose
Blood sugar measured after 8–12 hours without food. The standard test for diagnosing diabetes and prediabetes.
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What is Fasting Glucose?
Fasting glucose measures the amount of sugar (glucose) in your blood after you haven't eaten for at least 8 hours. This "baseline" reading shows how well your body manages blood sugar without the influence of recent meals.
It's the most common test for screening and diagnosing diabetes and prediabetes.
Normal Ranges
| Fasting Glucose | Classification |
|---|---|
| Below 100 mg/dL | Normal |
| 100–125 mg/dL | Prediabetes |
| 126+ mg/dL | Diabetes (requires confirmation) |
Why It Matters
Diabetes Diagnosis
Two fasting glucose readings of 126 mg/dL or higher confirms diabetes. Early detection allows treatment before complications develop.
Prediabetes Detection
The 100–125 mg/dL range identifies prediabetes — a critical window for lifestyle intervention. Many people can prevent progression to diabetes at this stage.
Daily Regulation
Even within "normal" ranges, higher fasting glucose is associated with increased health risks. Optimal is generally below 90 mg/dL.
Fasting Glucose vs. HbA1c
| Test | What It Shows |
|---|---|
| Fasting Glucose | Blood sugar at one moment |
| HbA1c | Average over 2–3 months |
Both are useful — glucose for acute changes, HbA1c for long-term patterns.
What Affects Fasting Glucose
- Sleep quality (poor sleep raises glucose)
- Stress (cortisol raises glucose)
- Dawn phenomenon (natural morning rise)
- Medications
- Recent illness