mg/dL vs mmol/L: What Your Blood Sugar Unit Actually Means

Your old glucometer was working fine for the past couple of years. But when you checked your recent lab reports, the readings of that meter seemed a bit inconsistent, so you ordered a new blood glucose monitor. Your new meter arrives and you test your blood sugar using a fresh strip. You wait for the countdown and the display says 5.9!

You freeze for a second. You were expecting the reading to be slightly below or over 100. Suddenly, many thoughts start popping up! Am I too ill? Is the meter alright? Did I get a bad one? Should I test again? Eat something? Take medication?

You’ve every right to be confused and anxious because the meter you are using is showing the blood sugar reading using a different unit than the one in your old meter. The 5.9 reading you saw would be 106 if we convert it to your old device’s unit. These two different units are called mmol/L and mg/dL, respectively. Consider them as two different temperature scales, the way Celsius and Fahrenheit are.

mg/dL vs mmol/L: What Do Blood Sugar Units Mean?

Blood glucose units primarily let you know how much sugar is present in a collected blood sample. Two of the most commonly used units in glucometers are milligrams per deciliter (mg/dL) and millimoles per liter (mmol/L).

The unit mg/dL tells you how much glucose is present in one deciliter (one-tenth of a liter) of blood, while mmol/L measures the amount of glucose in one liter of blood. Both units are different in how they express the results but describe the same glucose level in your blood. Put simply, they describe the same thing on different scales [1].

Let’s explain how. 

The Short Answer: One Number, 18

To convert one unit to the other, you just need to use the value 18. The exact conversion factor is about 18.01559, which is based on the molar mass of glucose (180.156 grams per mole) [2]. In everyday use, we round the factor to 18 to make things easier for blood sugar calculations.

mg/dL to mmol/L formula: mg/dL ÷ 18 = mmol/L (Example: 126 mg/dL ÷ 18 = 7.0 mmol/L)

mmol/L to mg/dL formula: mmol/L × 18 = mg/dL (Example: 6.5 mmol/L × 18 = 117 mg/dL)

Warning: The factor 18 works only for glucose. Do not use ×18 or ÷18 for hemoglobin A1c (HbA1c), blood ketones or uric acid. That’s because those tests measure different substances and have their own units.

Why Countries Still Use Different Blood Sugar Units

The reason is less clinical and more historical.

The International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) has long recommended reporting plasma glucose using the unit mmol/L, regardless of sample type or technology [3]. While most countries worldwide adopted the IFCC recommended unit decades ago, some countries such as the United States never switched from mg/dL to mmol/L, so mg/dL is still the standard unit there [4].

Hence, the safest choice is the unit used in your treatment plan and by the clinician who reviews your blood sugar readings. Before you order a new glucometer, check the unit option on the product page. If you are still unsure about which unit to go for, ask your doctor, pharmacist or local clinic which unit they use.

How to Tell Which Unit You Are Looking At

Never assume a high blood sugar reading is automatically mg/dL and a low reading is mmol/L. Your result can sometimes fall well outside the usual range, so always check the unit written next to the number. This simple step can save you from a lot of confusion. However, there are certain instances where you can easily tell which unit your home glucometer is showing.

Any reading above 34 is likely mg/dL. If a home meter uses the mmol/L unit, the maximum numeric reading it might display is 33.3 mmol/L (600 mg/dL), so any value above this number typically shows a “HI” or an error code. But if a meter shows a value above about 34, you may easily assume the built-in unit to be mg/dL. 

Below about 20 is probably mmol/L. In most meters with the mg/dL unit, the minimum numeric reading it might show is 20 mg/dL (1.1 mmol/L). Any value below this threshold often displays a “LO” or an error code.

The reading becomes ambiguous when it falls between 20 and 34. A value of 22 could be 22 mg/dL (1.1 mmol/L), which is a level 2 hypoglycemia reading (low blood sugar). In contrast, a reading of 22 mmol/L (396 mg/dL) indicates marked hyperglycemia (high blood sugar). Both readings need immediate medical attention but call for opposite responses. 

So, the best way forward is not to guess but to confirm which unit your meter is set to. If your meter shows a word rather than a reading, our guide to HI and LO readings explains what it means and what to do next. And if it shows a code, check out our error-code guide to understand the problem.

Do Not Confuse Your Glucometer’s Unit with HbA1c Units

HbA1c is a measure of average blood glucose exposure over the previous 2 to 3 months. However, it does not use the same glucose units as glucometers. It is expressed either as a percentage (%), which is standard in the United States, or in millimoles per mole (mmol/mol), used in the United Kingdom and elsewhere [5]. 

Many people confuse this mmol/mol unit with the mmol/L unit of glucometers. An HbA1c of 30 mmol/mol (4.9%) and a glucose reading of 30 mmol/L are unrelated numbers. The 30 mmol/mol result falls below the usual prediabetes threshold, whereas a 30 mmol/L reading means severe hyperglycemia and a medical emergency [6]. So, always check the full unit, not the first two letters.

Frequently Asked Questions (FAQs)

Is 5.6 the same as 101?

Yes. If the unit is mmol/L, then 5.6 × 18 = 100.8, and if we round the number, it will be 101 in the mg/dL unit. It’s the same result but expressed using two different units. 

Is mg/dL more accurate than mmol/L?

No. Both units reveal the same blood glucose level, so neither one is more accurate than the other. The difference between these two units is like the difference between Celsius and Fahrenheit scales. Both are used to measure temperature, and you can easily convert from one to the other. 

Can I identify the unit from the number alone?

No, you can’t! This is a very risky practice because if the reading falls between 20 and 34, it could be either mmol/L or mg/dL. So, check the unit on your meter’s screen.

What unit will my meter show if I buy it abroad?

It will largely depend on the country you’re buying it from. mg/dL is common in the United States and several other countries, while mmol/L is common in many other systems. Some use both. Check the specifications of the blood glucose monitor before ordering. 

My clinic gave me a number in the other unit. What do I do?

The simple answer is to convert the value to your preferred unit. Divide by 18 to convert mg/dL to mmol/L, and multiply by 18 to convert mmol/L to mg/dL. 

Which Unit Sinocare Blood Sugar Meters Use

All Sinocare blood glucose monitors come with two versions, one reading mg/dL and one reading mmol/L. The unit is set before the glucometer leaves the factory, and each meter displays only one unit. The setting is preset during manufacturing and cannot be changed by the user, so confirm the unit before testing.

Every meter in the Sinocare blood glucose meter range lets you choose your unit alongside the kit size. You cannot switch between units once purchased, so the unit you select at checkout is the unit you keep. If you are not sure which one you need, the Sinocare Measurement Unit and Quantity Help page walks you through the options. If your meter shows an unexpected unit, confirm the model and contact Sinocare support before changing your treatment based on the result.

References

1. Mathew TK, Zubair M. Blood glucose monitoring. In: StatPearls. Updated April 12, 2026. StatPearls Publishing; 2026. Accessed August 28, 2026. https://www.ncbi.nlm.nih.gov/books/NBK555976/ 
2. National Institute of Standards and Technology. Certificate of analysis: Standard Reference Material 965c, glucose in frozen human serum. Issued September 18, 2025. Accessed August 21, 2026. https://tsapps.nist.gov/srmext/certificates/965c.pdf
3. D'Orazio P, Burnett RW, Fogh-Andersen N, et al. Approved IFCC recommendation on reporting results for blood glucose. Clin Chem Lab Med. 2006;44(12):1486-1490. doi:10.1515/CCLM.2006.275 
4. Weinstock RS, Aleppo G, Bailey TS, et al. The Role of Blood Glucose Monitoring in Diabetes Management. American Diabetes Association; 2020. doi:10.2337/db2020-31 
5. Sacks DB, Arnold M, Bakris GL, et al. Guidelines and recommendations for laboratory analysis in the diagnosis and management of diabetes mellitus. Clin Chem. 2023;69(8):808-868. https://doi.org/10.1093/clinchem/hvad080
6. Mustafa OG, Haq M, Dashora U, Castro E, Dhatariya KK; Joint British Diabetes Societies (JBDS) for Inpatient Care Group. Management of hyperosmolar hyperglycaemic state (HHS) in adults: an updated guideline from the Joint British Diabetes Societies (JBDS) for Inpatient Care Group. Diabet Med. 2023;40(3):e15005. doi:10.1111/dme.15005