mmol/L to mg/dL Blood Sugar Converter
Convert blood glucose readings from mmol/L (used in the UK, Canada, Europe, and Australia) to mg/dL (used in the United States). Multiply mmol/L by 18.018 to get mg/dL.
Blood Sugar Reference Ranges: mmol/L and mg/dL
The following ranges are based on guidelines from the American Diabetes Association (ADA) and the World Health Organization (WHO). These apply to adults without pregnancy-related diabetes. Ranges may vary slightly between healthcare systems and individual patient circumstances.
| Status | mmol/L | mg/dL |
|---|---|---|
| Severe hypoglycemia | < 2.8 | < 50 |
| Hypoglycemia | < 3.9 | < 70 |
| Normal (fasting) | 3.9 – 5.5 | 70 – 99 |
| Prediabetes (fasting) | 5.6 – 6.9 | 100 – 125 |
| Diabetes (fasting) | ≥ 7.0 | ≥ 126 |
| Normal (2h post-meal) | < 7.8 | < 140 |
| Prediabetes (2h post-meal) | 7.8 – 11.0 | 140 – 199 |
| Diabetes (2h post-meal) | ≥ 11.1 | ≥ 200 |
| ADA target: fasting (diabetes) | 4.4 – 7.2 | 80 – 130 |
| ADA target: post-meal (diabetes) | < 10.0 | < 180 |
Sources: ADA Standards of Medical Care in Diabetes, WHO Diagnostic Criteria for Diabetes.
Worked Examples: mmol/L to mg/dL
Each example below shows a clinically meaningful blood glucose value, its mg/dL equivalent, and what that reading typically indicates. The formula is: mg/dL = mmol/L × 18.018.
Understanding Blood Glucose Units
Blood glucose concentration is measured in two units globally. The United States uses mg/dL (milligrams of glucose per deciliter of blood), while the United Kingdom, Canada, Australia, New Zealand, and most of Europe and Asia use mmol/L (millimoles of glucose per liter of blood).
The conversion factor — 18.018 — is derived from the molar mass of glucose. Glucose (C₆H₁₂O₆) has a molecular weight of approximately 180.18 grams per mole. To go from a molar concentration (mmol/L) to a mass concentration (mg/dL), you multiply by the molar mass and adjust for the unit difference between liters and deciliters (1 liter = 10 deciliters): 180.18 g/mol ÷ 10 = 18.018.
The practical implication: a reading of 7.0 mmol/L in a UK lab report is the same physiological value as 126 mg/dL on a US blood glucose report. Neither system is more accurate — they simply express the same concentration in different mathematical frameworks.
For people with diabetes who travel internationally or consult with healthcare providers in different countries, this conversion is critical. A glucometer calibrated in mmol/L will show completely different numbers than a US meter showing mg/dL — but both are measuring the same blood glucose concentration. Always verify which unit your device uses before interpreting results.
Why This Conversion Matters Clinically
The choice of blood glucose unit affects how people perceive their readings. In the US, "a blood sugar of 100" sounds normal (it is — that is 100 mg/dL, the upper bound of the normal fasting range). In the UK, "a blood sugar of 100" would be dangerously high — equivalent to 1,800 mg/dL, which is incompatible with life. Understanding that UK readings of 5–7 correspond to US readings of 90–126 prevents catastrophic misinterpretation.
People with type 1 or type 2 diabetes who travel internationally must be especially careful. A continuous glucose monitor (CGM) or glucometer may be set to the local unit. If a traveler from the US visits the UK and rents a meter that reads in mmol/L, they need to know that a reading of 5.5 mmol/L is healthy (99 mg/dL), not dangerously low as a US-trained patient might assume when they see a number below 70.
Medical literature, including clinical trial results and ADA/WHO guidelines, is published in both units. When reading research, always check which unit is being used and convert if necessary before applying guidelines to your personal management plan.
History of Blood Glucose Measurement Units
The first practical blood glucose test was developed in the early 20th century. By the mid-20th century, American clinical laboratories had standardized on mg/dL, while European laboratories, following the metric SI system more strictly, adopted mmol/L. The SI (International System of Units) recommends mmol/L as the proper unit for substance concentration in body fluids, which is why most countries outside the US use it.
The American Diabetes Association, the CDC, and US clinical labs have resisted switching to mmol/L primarily because of the enormous installed base of patient education materials, physician training, and home glucometers all calibrated in mg/dL. Switching units would require retraining millions of patients and healthcare providers, reprinting drug dosing guides, and recalibrating medical equipment.
The HbA1c test (glycated hemoglobin), which reflects average blood glucose over 2-3 months, is reported in percentage (%) in the US and in mmol/mol internationally. An A1C of 7% (US) equals 53 mmol/mol (international), using a different conversion than blood glucose. This adds a further layer of complexity for international patients and researchers.
Frequently Asked Questions
What is the formula to convert mmol/L to mg/dL?
Multiply the mmol/L value by 18.018 to get mg/dL. The factor 18.018 represents the molar mass of glucose (180.18 g/mol) divided by 10. For quick mental math, multiplying by 18 is accurate to within 0.1%.
What is a normal blood sugar level in mg/dL?
A normal fasting blood glucose is 70–99 mg/dL (3.9–5.5 mmol/L). Two hours after a meal, normal levels are below 140 mg/dL (7.8 mmol/L). These are the American Diabetes Association (ADA) reference ranges for adults without diabetes.
What is a normal blood sugar in mmol/L?
Normal fasting blood glucose is 3.9–5.5 mmol/L (70–99 mg/dL). Prediabetes ranges from 5.6–6.9 mmol/L (100–125 mg/dL). A diagnosis of diabetes requires a fasting level of 7.0 mmol/L (126 mg/dL) or higher on two separate occasions.
Why do the US and UK use different blood sugar units?
The United States uses mg/dL (milligrams per deciliter), while the UK, Canada, Australia, and most of Europe use mmol/L (millimoles per liter). The choice reflects which measurement framework was adopted when clinical laboratories were standardized in each country. Both units are scientifically equivalent — they simply express the same concentration differently.
How do I convert 5.6 mmol/L to mg/dL?
5.6 × 18.018 = 100.9 mg/dL, typically rounded to 101 mg/dL. A fasting reading of 5.6 mmol/L is the lower boundary of the prediabetes range (5.6–6.9 mmol/L / 100–125 mg/dL) according to ADA and WHO guidelines.
What blood sugar level indicates diabetes in mmol/L?
A fasting blood glucose of 7.0 mmol/L (126 mg/dL) or higher on two separate tests indicates diabetes, according to the American Diabetes Association. A random blood glucose of 11.1 mmol/L (200 mg/dL) or higher with symptoms of diabetes (frequent urination, excessive thirst, unexplained weight loss) also meets diagnostic criteria.
What is hypoglycemia in mmol/L?
Hypoglycemia (low blood sugar) is generally defined as a blood glucose below 3.9 mmol/L (70 mg/dL) in people with diabetes. Symptoms typically appear below 3.5 mmol/L (63 mg/dL) and may include shaking, sweating, confusion, and rapid heartbeat. Severe hypoglycemia (below 2.8 mmol/L / 50 mg/dL) is a medical emergency.
How accurate is the mmol/L to mg/dL conversion?
The conversion factor of 18.018 is derived from the exact molar mass of glucose (C₆H₁₂O₆ = 180.18 g/mol). The relationship is mathematically exact: 1 mmol/L = 18.018 mg/dL with no measurement uncertainty beyond the precision of the molar mass. Home glucometers have a measurement error of ±15-20% from true blood glucose, which is far larger than any rounding in the unit conversion itself.
What is a target blood sugar for people with diabetes?
Per ADA guidelines, the target fasting blood glucose for most non-pregnant adults with diabetes is 80–130 mg/dL (4.4–7.2 mmol/L). The target two hours after a meal is less than 180 mg/dL (10.0 mmol/L). Individual targets vary based on age, other conditions, and risk of hypoglycemia — always follow your healthcare provider's personalized recommendations.
Sources & References
- American Diabetes Association — Standards of Medical Care in Diabetes — Blood glucose targets and diagnostic criteria used in this page.
- World Health Organization — Use of Glycated Haemoglobin (HbA1c) in the Diagnosis of Diabetes Mellitus — WHO diagnostic criteria and glucose reference ranges.
- NCBI — Clinical Methods: Blood Glucose Testing — Clinical basis of blood glucose measurement and interpretation.
- Diabetes UK — Blood Sugar Level Ranges — UK (mmol/L) reference ranges and guidance.
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