mg/dL vs mmol/L: blood sugar units explained
mg/dL and mmol/L are two ways to write the same thing: how much glucose is in your blood. Divide a mg/dL number by 18 to get mmol/L, or multiply a mmol/L number by 18 to get mg/dL. For example, 100 mg/dL is about 5.5 mmol/L.
What is the difference between mg/dL and mmol/L?
Both units describe the concentration of glucose in blood. mg/dL means milligrams of glucose per decilitre of blood. mmol/L means millimoles of glucose per litre. Because the units are different, the same blood sugar looks like a very different number: about 18 times larger in mg/dL.
Which countries use which unit?
mg/dL is the usual unit in the United States and in many other countries. mmol/L is the usual unit in the United Kingdom, Canada, Australia and many countries in Europe and Asia. Your meter and your care team use one of them, so check the unit printed next to your number.
How do you convert between them?
Divide by about 18 to go from mg/dL to mmol/L. Multiply by about 18 to go the other way. The exact factor is 18.02. Use the blood sugar converter for instant results.
| mg/dL | mmol/L |
|---|---|
| 40 | 2.2 |
| 50 | 2.8 |
| 60 | 3.3 |
| 70 | 3.9 |
| 80 | 4.4 |
| 90 | 5.0 |
| 100 | 5.5 |
| 110 | 6.1 |
| 120 | 6.7 |
| 130 | 7.2 |
| 140 | 7.8 |
| 150 | 8.3 |
| 160 | 8.9 |
| 170 | 9.4 |
| 180 | 10.0 |
| 190 | 10.5 |
| 200 | 11.1 |
| 220 | 12.2 |
| 240 | 13.3 |
| 260 | 14.4 |
| 280 | 15.5 |
| 300 | 16.6 |
| 320 | 17.8 |
| 340 | 18.9 |
| 360 | 20.0 |
| 380 | 21.1 |
| 400 | 22.2 |
Why do unit mix-ups matter?
A reading of 7 makes sense in mmol/L but would be dangerously low in mg/dL, and 126 makes sense in mg/dL but cannot be a mmol/L reading. If a diary or an app guesses the wrong unit, averages and charts become wrong. Always write the unit with every reading.
Tips for logging the right unit
- Write the unit next to every number in a paper diary.
- Choose one unit in your app and check it matches your meter.
- If you travel or switch meters, note the change and the date.
Information, not medical advice. Talk to your care team about your own targets and treatment. Never use a converter or a diary entry to work out an insulin or medicine dose.
Sources
Frequently asked questions
Is 5.5 mmol/L the same as 100 mg/dL?
Almost. 100 mg/dL is about 5.55 mmol/L, which most meters round to 5.5 or 5.6. Using the exact factor of 18.02, 100 mg/dL is 5.549 mmol/L.
Can I change the unit on my meter?
Many meters can show either unit. Check the manual or ask your pharmacist or care team before changing it, and note the unit you use in your diary.
How does Glycove handle the two units?
Glycove saves every reading in the unit it was recorded in and shows your history in the unit you choose. It also warns you when a number looks like it belongs to the other unit.
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