mmol/L or mg/dL? Lab units explained
Why labs report the same test in different units, and a conversion table for glucose, cholesterol, creatinine, vitamin D, HbA1c and more.
Your glucose is 5.5 on one report and 99 on another. Your vitamin D is 75 here and 30 there. Nothing changed — the numbers are the same results written in two different unit systems. If you've moved country, used a different lab or compared notes with someone abroad, this can be genuinely confusing.
Two systems for the same measurement
Most of the world — including Canada, the UK, Europe and Australia — reports lab results in SI units (the International System of Units). These usually count how many molecules are present: millimoles or micromoles per litre (mmol/L, µmol/L).
The United States mostly uses conventional units, which usually measure weight in a volume: milligrams per decilitre (mg/dL), nanograms per millilitre (ng/mL).
Because molecules of different substances weigh different amounts, every test has its own conversion factor. There's no single rule — which is why a table helps.
Conversion table
To convert from SI to US conventional units, multiply by the factor. To go the other way, divide.
| Test | SI unit | US unit | SI × factor = US | Example |
|---|---|---|---|---|
| Glucose | mmol/L | mg/dL | × 18.0 | 5.5 mmol/L ≈ 99 mg/dL |
| Total, LDL, HDL cholesterol | mmol/L | mg/dL | × 38.67 | 3.4 mmol/L ≈ 131 mg/dL |
| Triglycerides | mmol/L | mg/dL | × 88.57 | 1.7 mmol/L ≈ 151 mg/dL |
| Creatinine | µmol/L | mg/dL | ÷ 88.4 | 88 µmol/L ≈ 1.0 mg/dL |
| Urea / BUN | mmol/L (urea) | mg/dL (BUN) | × 2.8 | 5.0 mmol/L ≈ 14 mg/dL |
| Calcium | mmol/L | mg/dL | × 4.0 | 2.4 mmol/L ≈ 9.6 mg/dL |
| Total bilirubin | µmol/L | mg/dL | ÷ 17.1 | 17 µmol/L ≈ 1.0 mg/dL |
| Hemoglobin, albumin | g/L | g/dL | ÷ 10 | 140 g/L = 14.0 g/dL |
| Vitamin D (25-OH) | nmol/L | ng/mL | ÷ 2.5 | 75 nmol/L ≈ 30 ng/mL |
| Vitamin B12 | pmol/L | pg/mL | × 1.355 | 300 pmol/L ≈ 407 pg/mL |
| Free T4 | pmol/L | ng/dL | ÷ 12.87 | 15 pmol/L ≈ 1.17 ng/dL |
| Ferritin | µg/L | ng/mL | same number | 50 µg/L = 50 ng/mL |
| TSH | mIU/L | µIU/mL | same number | 2.0 mIU/L = 2.0 µIU/mL |
Factors are rounded; labs may use slightly different ones. Always compare a result with the range printed on the same report.
HbA1c: percent or mmol/mol
HbA1c has its own two scales. Many countries report it as a percentage (the "NGSP" or "DCCT" scale), while the UK, much of Europe and others use mmol/mol (the "IFCC" scale). They're linked by a formula rather than a single factor:
% = 0.0915 × (mmol/mol) + 2.15
So 42 mmol/mol is about 6.0%, and 48 mmol/mol is about 6.5%.
Common mix-ups
- Comparing numbers across systems. A vitamin D of 30 and one of 75 can be the same result. Always check the unit before comparing.
- Urea versus BUN. SI reports measure urea; US reports measure the nitrogen in it (blood urea nitrogen). The factor above converts between them.
- g/L versus g/dL. Hemoglobin of 140 and 14.0 are the same result — a factor of ten.
- Decimal commas. Many countries write 5,6 for 5.6. It's the same number.
How SECURECORDS handles units
In SECURECORDS you choose SI or US units in Settings, and every result, range and chart is shown in your choice. You can switch at any time — your stored results never change, because they're kept in one consistent form behind the scenes. When you import a lab-report PDF, the units printed on the report are recognised (including mg/dL, mmol/L and IFCC HbA1c) and converted for you, and you check every value before it's saved.