Blood Sugar Converter
mg/dL
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mmol/L
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Range
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How Blood Sugar Conversion Works
Blood sugar (glucose) conversion is the process of translating glucose readings between the two measurement systems used worldwide: milligrams per deciliter (mg/dL) and millimoles per liter (mmol/L). According to the American Diabetes Association (ADA), approximately 537 million adults worldwide live with diabetes as of 2024, and many need to convert readings when traveling internationally, reading foreign medical literature, or using glucose monitors calibrated to the other system. The United States, Japan, France, Egypt, Colombia, and India use mg/dL, while most of Europe, Canada, Australia, China, and the United Kingdom use mmol/L. Both units are equally valid for clinical purposes. For related health assessments, check your A1C level and BMI.
The Conversion Formula
The conversion between mg/dL and mmol/L uses the molecular weight of glucose (C6H12O6), which is 180.16 g/mol. Since 1 deciliter equals 0.1 liters, the conversion factor becomes 180.16 / 10 = 18.016, typically rounded to 18.0 for clinical use. To convert from mg/dL to mmol/L, divide the mg/dL value by 18.0. To convert from mmol/L to mg/dL, multiply the mmol/L value by 18.0. For example, a fasting glucose of 100 mg/dL equals 100 / 18.0 = 5.56 mmol/L, and a reading of 7.0 mmol/L equals 7.0 x 18.0 = 126 mg/dL.
Normal Blood Sugar Ranges
Understanding where your reading falls on the clinical spectrum is just as important as converting between units. The following reference ranges are based on guidelines from the American Diabetes Association (ADA) and the World Health Organization (WHO).
| Category | Fasting (mg/dL) | Fasting (mmol/L) | 2-Hour Post-Meal (mg/dL) | 2-Hour Post-Meal (mmol/L) |
|---|---|---|---|---|
| Hypoglycemia (Low) | Below 70 | Below 3.9 | Below 70 | Below 3.9 |
| Normal | 70 - 99 | 3.9 - 5.5 | Below 140 | Below 7.8 |
| Pre-Diabetes | 100 - 125 | 5.6 - 6.9 | 140 - 199 | 7.8 - 11.0 |
| Diabetes | 126 or higher | 7.0 or higher | 200 or higher | 11.1 or higher |
A1C and Its Correlation to Average Blood Sugar
The A1C test (also called HbA1c or glycated hemoglobin) measures the percentage of hemoglobin proteins in red blood cells that have glucose attached to them. Because red blood cells live approximately 90 to 120 days, the A1C provides a weighted average of blood sugar over the past 2 to 3 months, with more recent weeks contributing more heavily. The formula for estimated average glucose (eAG) is: eAG (mg/dL) = (A1C x 28.7) - 46.7. Using this formula, an A1C of 5.0% corresponds to an average glucose of about 97 mg/dL (5.4 mmol/L), 6.0% to about 126 mg/dL (7.0 mmol/L), 7.0% to about 154 mg/dL (8.6 mmol/L), and 8.0% to about 183 mg/dL (10.2 mmol/L).
| A1C (%) | Estimated Avg Glucose (mg/dL) | Estimated Avg Glucose (mmol/L) | Interpretation |
|---|---|---|---|
| 5.0 | 97 | 5.4 | Normal |
| 5.6 | 114 | 6.3 | Normal (upper end) |
| 5.7 | 117 | 6.5 | Pre-diabetes begins |
| 6.4 | 137 | 7.6 | Pre-diabetes (upper end) |
| 6.5 | 140 | 7.8 | Diabetes threshold |
| 7.0 | 154 | 8.6 | Common diabetes target |
| 8.0 | 183 | 10.2 | Above target for most patients |
| 10.0 | 240 | 13.4 | Poorly controlled |
When and How to Test Blood Sugar
Fasting blood sugar tests should be performed after at least 8 hours without eating or drinking anything other than water. This test is typically done first thing in the morning and is the standard screening test for diabetes. Post-prandial (after-meal) testing is done 2 hours after the start of a meal and helps assess how well the body handles glucose after eating. For people with diabetes, self-monitoring with a home glucose meter involves pricking a fingertip with a lancet, placing a drop of blood on a test strip, and reading the result on a portable meter. Continuous glucose monitors (CGMs) like the Dexterity G7, Libre 3, and Medtronic Guardian use a small sensor inserted under the skin that measures interstitial glucose every 1 to 5 minutes, providing a real-time stream of readings and trend arrows.
Blood Sugar Targets for Diabetes Management
For most adults with diabetes, the ADA recommends a fasting or pre-meal target of 80 to 130 mg/dL (4.4 to 7.2 mmol/L) and a post-meal target below 180 mg/dL (10.0 mmol/L). However, targets are individualized based on age, duration of diabetes, comorbid conditions, and hypoglycemia risk. Pregnant women with gestational diabetes have tighter targets: fasting below 95 mg/dL (5.3 mmol/L), one-hour post-meal below 140 mg/dL (7.8 mmol/L), and two-hour post-meal below 120 mg/dL (6.7 mmol/L). Elderly patients or those with a history of severe hypoglycemia may have relaxed targets with an A1C goal below 8.0% rather than the standard 7.0%.
Factors That Affect Blood Sugar Readings
Blood sugar levels fluctuate throughout the day based on many factors beyond food intake. Stress hormones like cortisol and adrenaline raise blood sugar, which is why readings may spike during illness, emotional stress, or surgery. Physical exercise generally lowers blood sugar by increasing insulin sensitivity and glucose uptake into muscles, though intense exercise can temporarily raise levels due to counter-regulatory hormone release. Medications such as corticosteroids (prednisone), thiazide diuretics, and some antipsychotics can elevate blood sugar. Dehydration concentrates blood and may produce falsely high readings. Temperature extremes can also affect test strip accuracy -- most meters are calibrated for use between 50 and 104 degrees Fahrenheit (10 to 40 degrees Celsius).
Glucose Meter Accuracy and Calibration
Home glucose meters are required by the FDA to be within 15% of a laboratory reference value for readings at or above 75 mg/dL, and within 15 mg/dL for readings below 75 mg/dL. This means a meter reading of 100 mg/dL could represent a true value anywhere from 85 to 115 mg/dL. Some meters are calibrated to plasma glucose (the standard used in laboratories), while others report whole blood glucose, which is about 12% lower. Nearly all modern meters now report plasma-equivalent values for consistency with lab results. When converting between mg/dL and mmol/L, the mathematical conversion is exact, but the underlying measurement itself carries this inherent variability.
Frequently Asked Questions
What is the conversion factor between mg/dL and mmol/L?
The conversion factor is 18.016, derived from the molecular weight of glucose (180.16 g/mol) divided by 10. To convert mg/dL to mmol/L, divide by 18.016 (commonly rounded to 18.0). To convert mmol/L to mg/dL, multiply by 18.016. For example, 100 mg/dL equals approximately 5.6 mmol/L. This conversion is mathematically exact and applies equally to fasting, post-meal, and random glucose readings.
What is a normal fasting blood sugar level?
A normal fasting blood sugar is below 100 mg/dL (5.6 mmol/L) according to the ADA. Fasting levels between 100 and 125 mg/dL (5.6 to 6.9 mmol/L) indicate prediabetes (also called impaired fasting glucose), affecting an estimated 96 million American adults. A fasting level of 126 mg/dL (7.0 mmol/L) or higher on two separate tests is diagnostic of diabetes. For A1C correlations, see our A1C Calculator.
How does A1C relate to average blood sugar?
A1C reflects average blood glucose over 2 to 3 months by measuring the percentage of glycated hemoglobin in red blood cells. An A1C of 5.7% corresponds to roughly 117 mg/dL (6.5 mmol/L), 6.5% to about 140 mg/dL (7.8 mmol/L), and 7.0% to approximately 154 mg/dL (8.6 mmol/L). The formula is: estimated average glucose (mg/dL) = (A1C x 28.7) - 46.7. This formula was validated by the ADAG study published in Diabetes Care.
Why do different countries use different blood sugar units?
The United States, Japan, and some other countries use mg/dL (milligrams per deciliter), which measures mass of glucose per volume. Most of Europe, Canada, Australia, and China use mmol/L (millimoles per liter), the SI standard that measures molecular count per volume. Both are equally valid -- the difference is purely a matter of historical convention and does not affect clinical interpretation once converted. The WHO uses mmol/L in its official guidelines.
What blood sugar level is considered a medical emergency?
Blood sugar below 54 mg/dL (3.0 mmol/L) is classified as severe hypoglycemia and requires immediate treatment with fast-acting glucose (juice, glucose tablets, or glucagon injection). Blood sugar above 300 mg/dL (16.7 mmol/L) with symptoms like excessive thirst, frequent urination, or confusion may indicate diabetic ketoacidosis (DKA) or hyperosmolar hyperglycemic state (HHS), both of which require emergency medical care. The ADA recommends medical attention for any reading above 250 mg/dL (13.9 mmol/L) that does not respond to treatment within hours.
How accurate are home blood glucose meters?
Home glucose meters are required by the FDA to be within 15% of laboratory values for readings at or above 75 mg/dL, and within 15 mg/dL for readings below 75 mg/dL. A meter reading of 100 mg/dL could represent a true value between 85-115 mg/dL. Factors affecting accuracy include expired test strips, extreme temperatures, altitude, dirty or wet hands, and insufficient blood sample size. Continuous glucose monitors (CGMs) have similar accuracy but measure interstitial fluid with a 5-15 minute lag compared to blood glucose.