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Blood Sugar Converter – Free Glucose Unit Converter mg/dL to mmol/L

Convert blood glucose levels between mg/dL and mmol/L instantly. Enter a value in either unit to see the conversion in real-time. Essential tool for diabetes management.

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Conversion Formula

mmol/L = mg/dL ÷ 18

mg/dL = mmol/L × 18

Blood Sugar Reference Ranges

Fasting (normal):70-100 mg/dL (3.9-5.6 mmol/L)
Prediabetes:100-125 mg/dL (5.6-6.9 mmol/L)
Diabetes:≥126 mg/dL (≥7.0 mmol/L)
2hr after meal (normal):<140 mg/dL (<7.8 mmol/L)

How to Use This Blood Sugar Converter

1

Enter your blood glucose value

Type your reading in either the mg/dL or mmol/L field — conversion happens automatically.

2

View the converted value instantly

The other field updates in real-time with the converted measurement.

3

Compare with reference ranges

Use the reference table to understand where your reading falls within normal, prediabetes, or diabetes ranges.

Blood Glucose Reference Chart

Conditionmg/dLmmol/L
Hypoglycemia (Low)<70<3.9
Normal Fasting70-1003.9-5.6
Prediabetes (Fasting)100-1255.6-6.9
Diabetes (Fasting)≥126≥7.0
Normal (2hr after meal)<140<7.8
Prediabetes (2hr after meal)140-1997.8-11.0
Diabetes (2hr after meal)≥200≥11.1

Source: American Diabetes Association guidelines. Values may vary by laboratory and individual health status.

Understanding Blood Glucose Units

Why Two Different Units?

Blood glucose is measured in mg/dL (milligrams per deciliter) in the United States, Japan, India, and France. Most other countries use mmol/L (millimoles per liter). The difference is historical — mg/dL measures mass concentration, while mmol/L measures molar concentration.

The Conversion Factor

Glucose has a molecular weight of 180 g/mol. To convert mg/dL to mmol/L, divide by 18. To convert mmol/L to mg/dL, multiply by 18. This simple factor works because 1 mmol of glucose weighs 180 mg, and there are 10 deciliters in a liter.

When You Need to Convert

Conversion is useful when traveling abroad, reading international research, using imported glucose meters, or communicating with healthcare providers from different countries. Many modern glucose meters allow you to switch between units in the settings.

Tips for Blood Sugar Monitoring

Test at consistent times

Check fasting levels at the same time each morning. Test 2 hours after meals for postprandial readings.

Keep a log of your readings

Track your numbers along with meals, activity, and medication. Patterns help your doctor adjust treatment.

Wash hands before testing

Food residue on fingers can give falsely high readings. Use soap and water, then dry thoroughly.

Store test strips properly

Keep strips in their original container, away from heat and humidity. Expired strips give inaccurate results.

Frequently Asked Questions

What is a normal blood sugar level?
For people without diabetes, normal fasting blood sugar is 70-100 mg/dL (3.9-5.6 mmol/L). Two hours after eating, normal is below 140 mg/dL (7.8 mmol/L). Targets may differ for people with diabetes based on age, health status, and other factors.
When should I test my blood sugar?
Common testing times include: first thing in the morning (fasting), before meals, 2 hours after meals, before exercise, before driving, and at bedtime. Your doctor will recommend a testing schedule based on your treatment plan.
What causes high blood sugar?
High blood sugar (hyperglycemia) can result from eating too many carbohydrates, insufficient insulin or medication, illness, stress, lack of physical activity, or certain medications like steroids.
What is considered low blood sugar?
Blood sugar below 70 mg/dL (3.9 mmol/L) is considered low (hypoglycemia). Symptoms include shakiness, sweating, confusion, and irritability. Treat with 15 grams of fast-acting carbohydrate and recheck in 15 minutes.
Can I convert HbA1c to blood glucose?
HbA1c reflects average blood sugar over 2-3 months and uses different units (percentage). There are conversion formulas to estimate average glucose from HbA1c, but they provide approximations, not exact equivalents to fingerstick readings.

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