Conversion formula
mmol/L = mg/dL ÷ 18
mg/dL = mmol/L × 18
Blood sugar ranges
| Test | Normal | Prediabetes | Diabetes |
|---|---|---|---|
| Fasting | below 100 mg/dL (5.6 mmol/L) | 100 – 125 mg/dL | 126 mg/dL (7.0 mmol/L) or more |
| 2 hours after 75 g glucose (OGTT) | below 140 mg/dL (7.8 mmol/L) | 140 – 199 mg/dL | 200 mg/dL (11.1 mmol/L) or more |
| HbA1c | below 5.7% | 5.7 – 6.4% | 6.5% or more |
Low blood sugar
Below 70 mg/dL (3.9 mmol/L) is low blood sugar (hypoglycaemia). Symptoms include shaking, sweating, hunger and confusion. Take 15 g of fast sugar, such as glucose tablets or juice, wait 15 minutes and check again.
Frequently asked questions
What is normal fasting blood sugar?
Below 100 mg/dL (5.6 mmol/L).
What is normal blood sugar after eating?
For people without diabetes, usually below 140 mg/dL (7.8 mmol/L) two hours after a meal.
Can a single high reading mean diabetes?
No. Diabetes is diagnosed by a doctor, usually with repeat lab tests such as fasting glucose, OGTT or HbA1c.
Sources
- American Diabetes Association. Diagnosis of diabetes. Link
Medical disclaimer: This calculator gives estimates for general information only. It is not a diagnosis or a substitute for advice from a doctor or registered dietitian. Please consult a healthcare professional before making changes to your diet, exercise or medicines, especially if you are pregnant, have a medical condition or take regular medication.
Last updated: 20 October 2026. Read our editorial policy.
