mg/dL and mmol/L: two ways to measure blood sugar
Blood glucose is measured in two units. mg/dL (milligrams per decilitre) is used in the USA, the Gulf states, Pakistan, India and many other countries. mmol/L (millimoles per litre) is used in the UK, Europe, Canada and Australia, and appears on many lab reports. If you move between countries, read research or compare a meter with a lab result, you need to convert. This free blood sugar converter does it instantly and tells you what the number means.
How to convert blood sugar units
- mg/dL → mmol/L: divide by 18 (for example 126 ÷ 18 = 7.0 mmol/L)
- mmol/L → mg/dL: multiply by 18 (for example 5.5 × 18 = 99 mg/dL)
The factor 18 comes from the molecular weight of glucose (about 180 g/mol).
Normal blood sugar levels chart (adults without diabetes)
| Test | Normal | Prediabetes | Diabetes range |
|---|---|---|---|
| Fasting glucose | Under 100 mg/dL (5.6 mmol/L) | 100 – 125 mg/dL (5.6 – 6.9 mmol/L) | 126 mg/dL (7.0 mmol/L) or more |
| 2 hours after 75 g glucose (OGTT) | Under 140 mg/dL (7.8 mmol/L) | 140 – 199 mg/dL (7.8 – 11.0 mmol/L) | 200 mg/dL (11.1 mmol/L) or more |
| Random glucose | Usually under 140 mg/dL | — | 200 mg/dL or more with symptoms |
Low blood sugar (hypoglycaemia)
| Reading | Level |
|---|---|
| Under 70 mg/dL (3.9 mmol/L) | Low — level 1 hypoglycaemia |
| Under 54 mg/dL (3.0 mmol/L) | Very low — level 2, act immediately |
People with diabetes often aim for 80–130 mg/dL (4.4–7.2 mmol/L) before meals and under 180 mg/dL (10 mmol/L) 1–2 hours after meals (ADA), but your doctor may set different targets.
Benefits of understanding your readings
- Read any report or meter, wherever it was made.
- Spot patterns — for example high readings after rice-heavy dinners or sweet iftar drinks.
- Act quickly on lows and very high readings.
- Have better conversations with your doctor or dietitian.
Health warnings
- A single meter reading cannot diagnose diabetes. Diagnosis needs lab tests such as fasting glucose, OGTT or HbA1c.
- Home meters can be off by up to 15%. Wash and dry your hands before testing.
- Readings above 250–300 mg/dL (14–17 mmol/L) with vomiting, drowsiness or fast breathing need urgent care.
- Pregnancy has stricter targets — follow your obstetric team.
Food tips for steadier blood sugar
Pair carbohydrates with protein and fibre, choose low-GI foods (dal, chickpeas, oats, wholegrain roti), keep sweets and juices small and occasional, and walk after meals. See the glycemic load calculator and our guides to managing type 2 diabetes and insulin resistance.
Frequently asked questions
How do I convert mg/dL to mmol/L?
Divide the mg/dL value by 18. For example, 90 mg/dL ÷ 18 = 5.0 mmol/L.
How do I convert mmol/L to mg/dL?
Multiply the mmol/L value by 18. For example, 7.0 mmol/L × 18 = 126 mg/dL.
What is a normal fasting blood sugar?
For adults without diabetes, under 100 mg/dL (5.6 mmol/L) is normal. 100–125 mg/dL is prediabetes, and 126 mg/dL or more on two tests indicates diabetes.
What is normal blood sugar after eating?
Two hours after eating, blood sugar in people without diabetes is usually under 140 mg/dL (7.8 mmol/L).
What blood sugar level is dangerous?
Below 54 mg/dL (3.0 mmol/L) is dangerously low and needs immediate treatment. Very high readings, especially above 250–300 mg/dL with symptoms like vomiting or drowsiness, need urgent medical care.
Sources
- American Diabetes Association. Standards of Care in Diabetes — Diagnosis and classification; Glycemic goals and hypoglycemia.
- WHO. Definition and diagnosis of diabetes mellitus and intermediate hyperglycaemia. 2006.
- Diabetes UK. Blood sugar level ranges.