mg/dL to mmol/L Blood Glucose Conversion

Blood Glucose Converter

Convert blood sugar readings between mg/dL (milligrams per decilitre) and mmol/L (millimoles per litre). The UK uses mmol/L, whilst the US and some other countries use mg/dL.

mg/dL Value

mg/dL

mmol/L Value

mmol/L

Quick Conversions

Recent Conversions

mg/dL to mmol/L Conversion Table

This table shows common blood glucose values converted between both units. These values cover the typical range from low blood sugar (hypoglycaemia) to elevated levels.

mg/dL	mmol/L	Status
50	2.8	Low (Hypoglycaemia)
70	3.9	Low threshold
90	5.0	Normal fasting
100	5.6	Normal fasting
110	6.1	Normal
126	7.0	Diabetes threshold (fasting)
140	7.8	Upper target after meals
160	8.9	Elevated
180	10.0	High
200	11.1	Diabetes threshold (random)
250	13.9	Very high
300	16.7	Significantly elevated

Conversion Formula

Converting between these units is straightforward. The conversion factor is based on glucose’s molecular weight (180.16 g/mol).

mg/dL to mmol/L

mmol/L = mg/dL ÷ 18.0182

For example: 90 mg/dL ÷ 18.0182 = 5.0 mmol/L

mmol/L to mg/dL

mg/dL = mmol/L × 18.0182

For example: 5.0 mmol/L × 18.0182 = 90 mg/dL

Many people round the conversion factor to 18 for simplicity. Whilst this provides a close approximation, using 18.0182 gives more precise results.

Why Two Different Units?

The UK, Australia, and most of Europe measure blood glucose in mmol/L. This unit expresses the number of glucose molecules in a litre of blood. Meanwhile, the United States and Japan use mg/dL, which measures the weight of glucose per volume.

mmol/L is considered more scientifically precise because it accounts for the molecular nature of glucose. Both units are valid, but knowing how to convert between them helps when reading international medical literature or discussing results with healthcare providers abroad.

Normal Blood Glucose Ranges

For people without diabetes, blood glucose typically stays between 4.0 and 5.5 mmol/L (72-99 mg/dL) when fasting. After eating, levels may rise to 7.8 mmol/L (140 mg/dL) or slightly higher, then return to normal within a few hours.

Important: These ranges are general guidelines. Your healthcare provider may recommend different targets based on your individual circumstances, age, medications, and other health factors.

Diabetes Diagnostic Thresholds

According to WHO and NHS guidelines, diabetes is diagnosed when:

Fasting glucose: 7.0 mmol/L (126 mg/dL) or higher
Random glucose: 11.1 mmol/L (200 mg/dL) or higher with symptoms
Two hours after glucose load: 11.1 mmol/L (200 mg/dL) or higher
HbA1c: 48 mmol/mol (6.5%) or higher

Prediabetes (impaired glucose tolerance) is indicated by fasting levels between 5.6 and 6.9 mmol/L (100-125 mg/dL) or HbA1c between 42-47 mmol/mol (6.0-6.4%).

When to Monitor Your Levels

People with diabetes need regular monitoring to maintain proper glucose control. Those taking insulin typically test multiple times daily—before meals and at bedtime. People with type 2 diabetes not on insulin may test less frequently.

Anyone experiencing symptoms of high blood sugar (excessive thirst, frequent urination, fatigue) or low blood sugar (shakiness, confusion, sweating) should check their levels promptly. Pregnant women with gestational diabetes follow specific monitoring schedules recommended by their midwife or doctor.

Related Glucose Measurements

Measurement	Description	Normal Range
Fasting Plasma Glucose	Blood sugar after 8+ hours without food	4.0-5.5 mmol/L (72-99 mg/dL)
Random Glucose	Blood sugar at any time of day	Below 11.1 mmol/L (200 mg/dL)
Postprandial Glucose	Blood sugar 2 hours after eating	Below 7.8 mmol/L (140 mg/dL)
HbA1c	Average glucose over 2-3 months	Below 42 mmol/mol (6.0%)
Oral Glucose Tolerance Test	Blood sugar after 75g glucose drink	Below 7.8 mmol/L at 2 hours

FAQs

What’s the difference between mg/dL and mmol/L?

mg/dL measures the mass of glucose (in milligrams) per volume of blood (one decilitre). mmol/L measures the number of glucose molecules (in millimoles) per litre of blood. mmol/L is more scientifically precise, whilst mg/dL is simpler numerically.

Why does the UK use mmol/L instead of mg/dL?

The UK adopted mmol/L as part of the International System of Units (SI), which most countries use for medical measurements. This standardisation helps prevent confusion and errors in healthcare. The US continues using mg/dL as part of its traditional measurement system.

How do I convert my glucose meter if it shows the wrong units?

Most modern glucose metres allow you to change the display units in the settings menu. Check your device’s manual for specific instructions. If your metre doesn’t have this option, you’ll need to convert the readings manually using the formula: divide mg/dL by 18 to get mmol/L, or multiply mmol/L by 18 to get mg/dL.

What’s a dangerous blood sugar level?

Blood glucose below 3.0 mmol/L (54 mg/dL) indicates severe hypoglycaemia requiring immediate treatment. Levels above 15 mmol/L (270 mg/dL) suggest significant hyperglycaemia. Consistently high readings or levels above 20 mmol/L (360 mg/dL) need urgent medical attention. Always contact your healthcare provider if you’re concerned.

Should I test fasting or after meals?

It depends on your circumstances. Fasting tests (taken before breakfast) show your baseline glucose control. Postprandial tests (2 hours after eating) reveal how your body handles food. People with diabetes often do both. Your doctor or diabetes nurse will recommend a testing schedule suited to your needs.

Can stress affect my blood glucose readings?

Yes, stress triggers hormone release that can raise blood glucose levels. Physical stress (illness, injury) and emotional stress both affect readings. This is why healthcare providers look at patterns over time rather than single measurements. If you’re consistently stressed, discuss this with your doctor.

Are finger-prick tests as reliable as lab tests?

Home glucose metres are generally reliable for day-to-day monitoring, but lab tests are more precise. Metres can vary by ±15% and still meet accuracy standards. For diagnosis or when readings seem unusual, your doctor will order a laboratory blood test, which uses venous blood rather than capillary blood.

What’s the difference between plasma glucose and whole blood glucose?

Modern metres measure plasma glucose, which is 10-15% higher than whole blood glucose. Older devices measured whole blood. If you’re using an older metre, check whether it reports whole blood or plasma values, as this affects how you interpret results against current guidelines.

Medical Disclaimer: This converter provides information for educational purposes only. It’s not medical advice and shouldn’t replace professional healthcare guidance. Always consult your GP, diabetes nurse, or specialist for personalised recommendations about blood glucose monitoring and management.

References

World Health Organization. (2006). Definition and diagnosis of diabetes mellitus and intermediate hyperglycaemia: report of a WHO/IDF consultation. Geneva: World Health Organization.
World Health Organization. (2011). Use of glycated haemoglobin (HbA1c) in the diagnosis of diabetes mellitus. Abbreviated report of a WHO consultation. Geneva: World Health Organization.
Diabetes UK. (2025). Diagnostic criteria for diabetes. Available at: https://www.diabetes.org.uk/for-professionals/improving-care/clinical-recommendations-for-professionals/diagnosis-ongoing-management
National Institute for Health and Care Excellence. (2022). Type 2 diabetes in adults: management. NICE guideline [NG28]. London: NICE.
NHS England. (2019). Guidelines on self-monitoring of blood glucose use. London: NHS England.
International Diabetes Federation. (2008). Guideline for management of postmeal glucose in diabetes. Diabetes Research and Clinical Practice, 92(1), 4-8. doi: 10.1016/j.diabres.2008.09.048
Diabetes UK. (2022). Blood sugar level ranges. Available at: https://www.diabetes.co.uk/diabetes_care/blood-sugar-level-ranges.html
British Heart Foundation. (2024). Blood sugar levels: what is normal? Available at: https://www.bhf.org.uk/informationsupport/heart-matters-magazine/medical/tests/blood-sugar