Blood test units explained: mg/dL vs mmol/L and how to convert
Labs in the United States mostly report in conventional units such as mg/dL, while most other countries use SI units such as mmol/L. The numbers look very different, but they measure the same thing.
Common conversions
| Test | From SI unit | To US unit |
|---|---|---|
| Glucose | mmol/L × 18.0 | mg/dL |
| Total, LDL and HDL cholesterol | mmol/L × 38.67 | mg/dL |
| Triglycerides | mmol/L × 88.57 | mg/dL |
| Creatinine | µmol/L ÷ 88.4 | mg/dL |
| Vitamin D (25-hydroxy) | nmol/L ÷ 2.496 | ng/mL |
| Testosterone, total | nmol/L × 28.84 | ng/dL |
| Estradiol | pmol/L ÷ 3.671 | pg/mL |
| Vitamin B12 | pmol/L ÷ 0.738 | pg/mL |
| Insulin | pmol/L ÷ 6 (some labs use 6.945) | µIU/mL |
| Hemoglobin | g/L ÷ 10 | g/dL |
| Hemoglobin A1c | % = 0.0915 × (mmol/mol) + 2.15 | % (NGSP) |
Examples: a glucose of 5.5 mmol/L is about 99 mg/dL; a vitamin D of 75 nmol/L is about 30 ng/mL; an A1c of 39 mmol/mol is about 5.7%.
Units that are the same number
- Ferritin: ng/mL = µg/L.
- TSH: mIU/L = µIU/mL.
- Blood counts: x10E3/uL = K/uL = 109/L (white cells, platelets), and x10E6/uL = 1012/L (red cells).
Units you cannot convert
Lipoprotein(a) is reported either in nmol/L (number of particles) or mg/dL (mass). Because particle size varies from person to person, there is no reliable conversion between the two. Compare Lp(a) results only in the same unit.
Let the app do it
UnitedMarkers converts results to one unit per marker automatically, so results from different labs and countries line up on the same chart, while the original value and unit are always kept.
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This guide is educational and does not replace advice from a healthcare professional.