🩸 Blood Sugar Converter: mg/dL to mmol/L and Back

What is the Blood Sugar Converter?

Blood sugar, or blood glucose, is reported in two different units depending on where you live, and that is the single reason a blood sugar converter is so useful. The United States, Germany and a handful of other countries report glucose in milligrams per deciliter (mg/dL), while most of the rest of the world, including the United Kingdom, Canada, Australia and most of Europe, uses millimoles per liter (mmol/L). The underlying amount of sugar in the blood is identical, only the scale is different, much like measuring the same distance in miles or kilometers.

The two units are linked by the molar mass of glucose. One millimole of glucose weighs about 18.0182 milligrams, so a value in mmol/L is converted to mg/dL by multiplying by 18.0182, and a value in mg/dL is converted to mmol/L by dividing by the same number. Because the factor is close to 18, a quick mental estimate is to multiply mmol/L by 18 to approximate mg/dL, or divide mg/dL by 18 to approximate mmol/L. This blood sugar converter uses the precise factor so the result matches what a lab or meter would print rather than a rough guess.

Knowing the right unit matters because the numbers look alarmingly different even though they describe the same blood. A normal fasting glucose of 90 mg/dL is the same as 5.0 mmol/L. A reading of 5.0 in a country that uses mg/dL would be a medical emergency, while 90 in a country that uses mmol/L is not a real glucose value at all. Mixing up the units is one of the most common and most dangerous mistakes people make when comparing notes across borders, reading older medical literature or setting up an imported glucose meter, which is exactly what a converter prevents.

The meaning of a converted number depends heavily on the context of the reading. Fasting values, taken after at least eight hours without food, are interpreted differently from post-meal (postprandial) values, which are usually checked one to two hours after eating, and from random readings taken at any time. The general fasting reference bands for non-pregnant adults are normal below 100 mg/dL (5.6 mmol/L), prediabetes from 100 to 125 mg/dL (5.6 to 6.9 mmol/L), and diabetes at 126 mg/dL (7.0 mmol/L) or above on a repeated test. After meals the same person can rise well above their fasting number and still be in a healthy range, so a single converted figure is only meaningful when you know when and how it was measured.

This converter only changes units, it does not change what the value means for your health, and that distinction is important. Converting 250 mg/dL to 13.9 mmol/L does not make a high reading any lower, it simply expresses the same high reading in the other scale. The reference band shown alongside the result is a general guide to help you orient a fasting number, not a diagnosis. Glucose targets are personal and depend on age, type of diabetes, pregnancy, medication and other conditions, so the bands here are a starting point for a conversation with your care team rather than a verdict.

A blood sugar converter is handy in everyday situations far beyond a clinic. Travelers carry meters and prescriptions across regions that use different units, diabetes forums and apps mix mg/dL and mmol/L freely, recipes and research papers quote one or the other, and family members in different countries compare readings over the phone. Rather than reaching for a calculator and remembering whether to multiply or divide by roughly 18, you can paste either number here and read the equivalent at a glance, in the unit that makes sense to you.

When to use it

• Converting a lab glucose result in mg/dL into the mmol/L figure your country or app uses, or the reverse.
• Setting up an imported or secondhand glucose meter that displays the unit you are not used to.
• Comparing blood sugar readings with family or friends who live where the other unit is standard.
• Reading diabetes research, forums or older medical notes that quote glucose in the unfamiliar unit.
• Translating a fasting number while traveling so you can tell which general reference band it falls in.
• Double-checking a value before logging it in a tracker that expects a specific unit.

How to use the Blood Sugar Converter

1. Type your glucose reading into the box for the unit you already have, either mg/dL or mmol/L.
2. The other box fills in instantly with the converted value, rounded to a sensible number of places.
3. Read the converted figure in both mg/dL and mmol/L in the result line.
4. Check the reference note to see which general fasting band the value falls in.
5. Clear the box or type a new number to convert another reading, as many times as you like.

Formula & method

Worked examples

Blood sugar conversion chart: mg/dL to mmol/L

Reverse conversion: mmol/L to mg/dL

General fasting glucose reference ranges (non-pregnant adults)

Common mistakes to avoid

• Mixing up which unit a number is in. A value like 5.6 is a healthy mmol/L reading but a meaningless mg/dL one, while 100 is a normal mg/dL reading but an impossible mmol/L one. Always confirm which unit a number is in before converting or comparing it.
• Multiplying when you should divide. To go from mg/dL to mmol/L you divide by 18.0182, and to go the other way you multiply. Doing it backwards turns a normal number into an extreme one. Let the converter handle the direction for you.
• Thinking conversion changes the result. Converting 250 mg/dL to 13.9 mmol/L does not lower a high reading. It is the same blood sugar expressed on a different scale, so a high value stays high in both units.
• Comparing readings taken at different times. A fasting value and a post-meal value are interpreted differently. Converting the units does not make a reading taken an hour after eating comparable to one taken before breakfast.
• Treating the reference band as a diagnosis. The normal, prediabetes and diabetes bands shown here are general fasting guides. A diagnosis needs repeated testing and a clinician, not a single converted number.
• Over-rounding the mmol/L value. mmol/L readings are usually given to one decimal place, such as 5.6 rather than 6. Rounding to a whole number loses meaningful precision at the low values that this unit uses.

Glossary

Blood glucose

The amount of sugar (glucose) in your blood, the value that a blood sugar converter expresses in either mg/dL or mmol/L.

mg/dL

Milligrams per deciliter, the glucose unit used mainly in the United States and a few other countries.

mmol/L

Millimoles per liter, the glucose unit used in most of the world outside the United States.

Conversion factor

The number 18.0182, the molar mass of glucose, used to convert between mg/dL and mmol/L.

Fasting glucose

A blood sugar reading taken after at least eight hours without food, used for the standard reference ranges.

Postprandial glucose

A reading taken after a meal, usually one to two hours later, which is normally higher than a fasting value.

Prediabetes

A range where blood sugar is higher than normal but not yet diabetes, a fasting value of 100 to 125 mg/dL (5.6 to 6.9 mmol/L).

Millimole

A unit of amount of substance equal to one thousandth of a mole, the basis of the mmol/L scale.

Frequently asked questions

Sources

• Classification and Diagnosis of Diabetes, Standards of Care , American Diabetes Association, Diabetes Care
• Diabetes Tests and Diagnosis , National Institute of Diabetes and Digestive and Kidney Diseases