What is a Blood Glucose Unit Converter?
The blood glucose unit converter switches blood sugar readings between mg/dL and mmol/L — useful for comparing international medical sources or imported glucose meters.
How it's calculated
mg/dL ÷ 18 = mmol/L
mmol/L × 18 = mg/dL
The number 18 comes from glucose's molecular weight (180).
Units that are easy to mix up
| Units | Why it's confusing | How to tell them apart |
|---|---|---|
| mg/dL vs mmol/L | Different national standards | The US and a few other countries use mg/dL; the UK and most of Europe use mmol/L |
Why do countries use different units?
It comes down to measuring by mass versus by molecule count. mg/dL measures the mass of glucose in a volume of blood, while mmol/L counts glucose molecules directly. The US and a few other countries use mg/dL, while the UK, Canada, Australia, and most of Europe use mmol/L.
Good to know
- Normal fasting glucose is roughly 70–99 mg/dL (3.9–5.5 mmol/L). Levels of 100–125 indicate impaired fasting glucose, and 126+ on repeated tests suggests diabetes.
- HbA1c (hemoglobin A1c) reflects average blood sugar over the past 2–3 months, because red blood cells live about 120 days.
- Home glucose meters can differ slightly from lab results because they measure capillary whole blood, while labs typically measure venous plasma.
- The medical term diabetes mellitus combines Greek for 'to pass through' with Latin for 'honey-sweet' — a reference to how the condition was historically diagnosed by tasting sweet urine.
- Stress and poor sleep alone can raise blood sugar, since cortisol triggers the liver to release glucose — which is why a poor night's sleep can show up as a higher-than-usual fasting reading.
Frequently asked questions
Q. What is 100 mg/dL in mmol/L?
About 5.6 mmol/L. Divide by 18.
Q. What is the normal blood sugar range?
Fasting levels of 70–99 mg/dL (3.9–5.5 mmol/L) are considered normal, but diagnosis requires repeated testing and medical judgment.
Q. Why do home meters and lab tests give different readings?
They test different blood samples (capillary vs. venous) using different methods, so some variation is expected. Diagnosis should rely on laboratory testing.