Blood sugar (glucose) ranges
Blood glucose is measured in mg/dL (US) or mmol/L (most of the world). Fasting and 2-hour post-meal values diagnose prediabetes and diabetes; HbA1c reflects the average over about three months.
| State | mg/dL | mmol/L | Notes |
|---|---|---|---|
| Severe hypoglycemia | <54 | <3.0 | Seek medical help immediately |
| Hypoglycemia | 54–69 | 3.0–3.8 | Treat with 15 g fast-acting carbs |
| Normal (fasting) | 70–99 | 3.9–5.5 | Healthy fasting range |
| Normal (2h post-meal) | <140 | <7.8 | Standard postprandial target |
| Prediabetes (fasting) | 100–125 | 5.6–6.9 | Impaired fasting glucose |
| Prediabetes (2h post-meal) | 140–199 | 7.8–11.0 | Impaired glucose tolerance |
| Diabetes (fasting) | ≥126 | ≥7.0 | Confirm with a repeat test |
| Diabetes (2h post-meal) | ≥200 | ≥11.1 | Diagnosed via glucose tolerance test |
| HbA1c normal | <5.7% | <39 mmol/mol | 3-month average glucose |
| HbA1c diabetes | ≥6.5% | ≥48 mmol/mol | Diagnostic threshold |
Notes
- This is a general reference, not medical advice — always confirm results with a clinician.
- mmol/L = mg/dL x 0.0555; to convert back, mg/dL = mmol/L x 18.0.
- A single high reading is not a diagnosis; diabetes needs two abnormal tests or an HbA1c >= 6.5%.
- Symptoms of very low sugar (shaking, confusion) need fast carbs and medical care if severe.
Frequently asked questions
- What is a normal fasting blood sugar?
- A healthy fasting level is 70–99 mg/dL (3.9–5.5 mmol/L). Values of 100–125 mg/dL are prediabetes and 126 or above suggest diabetes.
- What is the 2-hour post-meal target?
- Under 140 mg/dL (7.8 mmol/L) two hours after eating is normal; 140–199 is prediabetes and 200 or more points to diabetes.
- How do I convert mg/dL to mmol/L?
- Multiply mg/dL by 0.0555 to get mmol/L (for example 100 mg/dL ≈ 5.6 mmol/L). To go back, multiply mmol/L by 18.0.
- What does HbA1c 6.5% mean?
- HbA1c of 6.5% or higher (>= 48 mmol/mol) is the diagnostic cutoff for diabetes and reflects average glucose over the past 2–3 months.