Conversion factors by test
Blood Glucose
Blood sugar (plasma glucose) from a lab test or meter.
Glucose has a molar mass of 180.16 g/mol, so 1 mmol/L = 18.016 mg/dL. mg/dL × 0.0555 = mmol/L.
Example: 100 mg/dL = 5.5506 mmol/L
mg/dL is standard in the US; mmol/L in the UK, Canada, Australia and most of Europe.
- Many meters and labs round the factor to 18, so 5.5 mmol/L may appear as 99 mg/dL or 99.1 mg/dL.
- HbA1c (% or mmol/mol) is a different test and needs a different formula; it is not converted here.
Cholesterol
Total, LDL or HDL cholesterol.
Cholesterol has a molar mass of 386.65 g/mol, so 1 mmol/L = 38.67 mg/dL. mg/dL × 0.02586 = mmol/L.
Example: 200 mg/dL = 5.172 mmol/L
mg/dL in the US; mmol/L in the UK, Canada, Australia and Europe.
- Triglycerides use a different factor (about 88.57 mg/dL per mmol/L); do not use the cholesterol factor for them.
Hemoglobin
Haemoglobin concentration in a blood count.
1 g/dL = 10 g/L. For mmol/L the per-haem (monomer) molar mass of 16,114 g/mol is used: 1 mmol/L = 1.6114 g/dL.
Example: 13.5 g/dL = 135 g/L
g/dL in the US; g/L in the UK, Canada and Australia; mmol/L mainly in the Netherlands.
- Some older literature uses the tetramer molar mass (about 64,458 g/mol), which gives mmol/L values four times smaller.
Creatinine
Serum creatinine, used to estimate kidney function.
Creatinine has a molar mass of 113.12 g/mol, so 1 mg/dL = 88.4 µmol/L.
Example: 1 mg/dL = 88.402 µmol/L
mg/dL in the US; µmol/L in the UK, Canada, Australia and Europe.
- eGFR equations expect creatinine in a specific unit; converting the result does not convert the eGFR.
BUN (Blood Urea Nitrogen)
Blood urea nitrogen — the nitrogen part of urea in the blood.
Each urea molecule carries two nitrogen atoms (2 × 14.007 g/mol), so 1 mmol/L of urea = 2.8014 mg/dL of urea nitrogen. BUN mg/dL × 0.357 = urea mmol/L.
Example: 15 mg/dL = 5.3545 mmol/L
BUN in mg/dL in the US; urea in mmol/L in the UK, Australia and Europe.
- Some countries report urea itself in mg/dL rather than urea nitrogen: urea mg/dL = BUN mg/dL × 2.14.
Liver (ALT/AST)
Liver enzyme activity (ALT, AST and other enzymes reported in U/L).
One enzyme unit (U) is 1 µmol of substrate per minute and the katal is 1 mol per second, so 1 µkat/L = 60 U/L and 1 U/L = 0.0167 µkat/L.
Example: 40 U/L = 0.66667 µkat/L
U/L almost everywhere; µkat/L in some Scandinavian laboratories.
- Enzyme activity depends on the assay temperature and method, so reference ranges from different labs are not interchangeable even in the same unit.
Electrolytes (Na/K)
Sodium and potassium in blood.
For ions with a single charge, mmol/L and mEq/L are equal. mg/dL × 10 ÷ atomic weight = mmol/L (sodium 22.990, potassium 39.098).
Example: 140 mmol/L / mEq/L = 321.86 mg/dL (Sodium)
mmol/L or mEq/L almost everywhere; mg/dL is rare for these tests.
- mEq/L equals mmol/L only for single-charge ions. For calcium or magnesium (charge 2), 1 mmol/L = 2 mEq/L.
Vitamin D
25-hydroxyvitamin D, the usual blood test for vitamin D status.
25-hydroxyvitamin D3 has a molar mass of 400.64 g/mol, so 1 ng/mL = 2.496 nmol/L and 1 nmol/L = 0.4006 ng/mL.
Example: 30 ng/mL = 74.88 nmol/L
ng/mL in the US; nmol/L in the UK, Canada, Australia and Europe.
- The factor is for total 25(OH)D (the D3 form). The D2 form alone converts at 2.423.
Calcium
Total calcium in blood.
Calcium has an atomic weight of 40.078, so 1 mmol/L = 4.008 mg/dL. mg/dL × 0.2495 = mmol/L.
Example: 9.5 mg/dL = 2.3704 mmol/L
mg/dL in the US; mmol/L in the UK, Canada, Australia and Europe.
- Calcium carries two charges, so 1 mmol/L = 2 mEq/L.
- Ionised (free) calcium is reported separately and has its own reference range.
TSH (Thyroid)
Thyroid-stimulating hormone.
A prefix conversion only: 1 IU/L = 1,000 mIU/L. mIU/L and µIU/mL are numerically identical.
Example: 2.5 mIU/L = 0.0025 IU/L
mIU/L or µIU/mL in most laboratories.
- TSH is measured in international units defined by a WHO reference preparation, so it cannot be converted to a mass unit.
Each factor was recalculated from the analyte's molar mass (PubChem, IUPAC atomic weights) and compared with published clinical conversion tables (Young 1987; Mayo Clinic Laboratories). An automated check recalculates every factor from the chemical formula on each build.
