Understanding mg/dL and mmol/L Units
Medical laboratories measure substances in blood using specific units. Two common units for reporting lab results are mg/dL and mmol/L.
mg/dL, or milligrams per deciliter, measures the weight of a substance in a specific volume of blood. One deciliter equals 100 milliliters, and this unit is common in the United States, Japan, and a few other countries.
mmol/L, or millimoles per liter, measures the number of molecules in a specific volume of blood. This unit is common throughout Europe, Canada, Australia, and many other countries.
Both units describe the same lab value in different ways, similar to miles and kilometers describing the same distance. Understanding both systems helps when reading international medical literature, comparing lab reports, or using medical devices from different countries.
How to Convert mg/dL to mmol/L
Converting mg/dL to mmol/L requires the molecular weight of the substance being measured. Each molecule has a unique molecular weight, so glucose, cholesterol, triglycerides, and creatinine cannot all use the same conversion factor.
Select the substance from the dropdown menu above. The calculator loads the correct conversion factor automatically. Then enter your mg/dL value and review the mmol/L result. For the reverse direction, switch to the mmol/L to mg/dL tab.
Conversion Formula Explained
The mg/dL to mmol/L formula uses molecular weight:
mmol/L = (mg/dL x 10) / molecular weight Because the conversion factor is molecular weight divided by 10, the same formula is often written as:
mmol/L = mg/dL / conversion factor For glucose, the molecular weight is 180.16 g/mol. To convert 100 mg/dL of glucose: 100 x 10 / 180.16 = 5.55 mmol/L.
Common Substance Conversion Factors
Different substances require different conversion factors based on molecular weight. Use the correct molecule before comparing values across reports or reference ranges.
| Molecule | Molecular weight | mg/dL to mmol/L | Medical use |
|---|---|---|---|
| Glucose | 180.16 g/mol | Divide by 18.016 | Blood sugar monitoring and diabetes management |
| Cholesterol (Total) | 386.65 g/mol | Divide by 38.665 | Cardiovascular risk assessment |
| HDL Cholesterol | 386.65 g/mol | Divide by 38.665 | Good cholesterol measurement |
| LDL Cholesterol | 386.65 g/mol | Divide by 38.665 | Bad cholesterol measurement |
| Triglycerides | 885.57 g/mol | Divide by 88.557 | Lipid panel evaluation |
| Urea (BUN) | 60.06 g/mol | Divide by 6.006 | Kidney function and protein metabolism assessment |
| Creatinine | 113.12 g/mol | Divide by 11.312 | Kidney function evaluation |
| Uric Acid | 168.11 g/mol | Divide by 16.811 | Gout and kidney stone evaluation |
| Calcium | 40.08 g/mol | Divide by 4.008 | Bone health and metabolic assessment |
| Magnesium | 24.31 g/mol | Divide by 2.431 | Electrolyte balance assessment |
Blood Glucose Conversion Chart
Blood glucose is one of the most frequently converted lab values. People monitoring diabetes often need to understand both mg/dL and mmol/L.
| mg/dL | mmol/L | Status |
|---|---|---|
| 70 | 3.9 | Low normal |
| 80 | 4.4 | Normal |
| 90 | 5.0 | Normal |
| 100 | 5.6 | Normal |
| 110 | 6.1 | Slightly elevated |
| 126 | 7.0 | Diabetic threshold (fasting) |
| 140 | 7.8 | Prediabetic/post-meal reference |
| 180 | 10.0 | Target maximum for many diabetics |
| 200 | 11.1 | Diabetic threshold (random) |
| 250 | 13.9 | High |
| 300 | 16.7 | Very high |
| 400 | 22.2 | Dangerously high |
Quick reference: normal fasting glucose is often about 70-100 mg/dL (3.9-5.6 mmol/L), prediabetes is often 100-125 mg/dL (5.6-6.9 mmol/L), and diabetes diagnosis is commonly 126 mg/dL or higher (7.0 mmol/L or higher) when fasting. For the full fasting and OGTT ranges, use the dedicated blood glucose conversion calculator. If you are reviewing longer-term diabetes markers, compare this with the HbA1c Conversion Calculator or HOMA-IR Calculator.
Cholesterol mg/dL to mmol/L Conversion
Cholesterol uses a different conversion factor than glucose. Total cholesterol, LDL cholesterol, and HDL cholesterol all use about 38.665 for mg/dL to mmol/L conversion, so divide your mg/dL value by 38.665 to get mmol/L. For a lipid-panel converter with desirable, borderline and high reference ranges, use the dedicated cholesterol conversion calculator. Triglycerides are the exception in a lipid panel — they use 88.57, not 38.67, so divide mg/dL by 88.57 with the dedicated triglycerides conversion calculator.
| mg/dL | mmol/L | Total cholesterol status |
|---|---|---|
| 150 | 3.88 | Optimal |
| 180 | 4.65 | Desirable |
| 200 | 5.17 | Borderline |
| 220 | 5.69 | Borderline high |
| 240 | 6.21 | High |
| 280 | 7.24 | Very high |
LDL targets are often discussed as below 100 mg/dL (2.6 mmol/L) for optimal, 130-159 mg/dL (3.4-4.1 mmol/L) for borderline high, and 190 mg/dL or higher (4.9 mmol/L or higher) for very high. HDL below 40 mg/dL (1.0 mmol/L) is commonly considered low.
Uric Acid mg/dL to mmol/L Conversion
Uric acid uses a conversion factor of about 16.811, so divide the mg/dL value by 16.811 to get mmol/L. Note that many labs report uric acid in µmol/L for these smaller concentrations, which is 1,000 times the mmol/L value (for example, 0.42 mmol/L equals 420 µmol/L).
| mg/dL | mmol/L | Uric acid status |
|---|---|---|
| 5 | 0.30 | Normal |
| 6 | 0.36 | Upper normal (female) |
| 7 | 0.42 | Upper normal (male) |
| 8 | 0.48 | Elevated |
| 9 | 0.54 | High |
| 10 | 0.59 | Very high |
Other Lab Value Conversions
Beyond glucose and cholesterol, many other lab values may need conversion between mg/dL and mmol/L.
- Triglycerides: below 150 mg/dL is about below 1.7 mmol/L.
- Blood Urea Nitrogen (BUN): 7-20 mg/dL is about 2.5-7.1 mmol/L.
- Creatinine: often reported internationally in µmol/L rather than mmol/L. Use the creatinine-specific calculator for kidney lab reports, or the Creatinine Clearance Calculator when you need a Cockcroft-Gault CrCl estimate.
- Uric acid: often reported internationally in µmol/L for smaller concentrations.
- Calcium: 8.5-10.5 mg/dL is about 2.1-2.6 mmol/L. For calcium plus mEq/L, use the Calcium Conversion Calculator.
Why Different Countries Use Different Units
The split between mg/dL and mmol/L has historical roots. The United States established many laboratory standards using mass-based units, while many other countries later adopted SI units that favor molar concentrations.
Neither system is inherently better for patients when used correctly. Both can describe the same lab result accurately, but the numbers differ because one system measures mass concentration and the other measures molar concentration.
When to Use This Converter
This mg/dL to mmol/L conversion calculator is useful when traveling abroad, reading international research, using imported medical devices, comparing lab reports from different countries, or communicating with healthcare providers who use a different unit system.
If your lab value is already in mmol/L, use the mmol/L to mg/dL conversion calculator. If you are combining fasting glucose with fasting insulin, use the HOMA-IR calculator.
Frequently Asked Questions
What is the easiest way to convert mg/dL to mmol/L for glucose?
For glucose, divide the mg/dL value by about 18. For example, 180 mg/dL divided by 18 is about 10 mmol/L. The calculator uses a more precise glucose factor of 18.016.
Is 7 mmol/L the same as 126 mg/dL?
Yes, for blood glucose these values are equivalent. A fasting glucose of 7.0 mmol/L is approximately 126 mg/dL.
Can I use the same conversion factor for all substances?
No. Each substance has a unique molecular weight, which creates a unique conversion factor. Always select the correct molecule.
What is the difference between mmol/L and µmol/L?
They differ by a factor of 1,000. One mmol/L equals 1,000 µmol/L. Substances measured in smaller concentrations, such as creatinine and bilirubin, often use µmol/L.
How accurate is this calculator?
The calculator uses standard molecular weights and accepted conversion formulas. It is useful for unit conversion, but medical decisions should always be reviewed with a qualified healthcare provider.
Can I convert A1C percentage to mmol/mol here?
No. A1C uses a different formula and is not the same as converting glucose concentration between mg/dL and mmol/L.
Final Thoughts
Converting mg/dL to mmol/L becomes simple once you use the correct molecule-specific factor. The calculator eliminates manual arithmetic and gives instant results for common lab values.
Both units measure the same substance in your blood. The number changes because the unit system changes, but the underlying health information is the same. Always discuss lab results with your healthcare provider for proper interpretation.