Blood Test Units Explained
Why your glucose looks like “5.0” in Australia and “90” on an American website - and the simple conversions to fix it.
SI vs Conventional Units - Why There Are Two
Australia, the UK, Canada and most of the world use SI units - the international scientific standard based on moles, litres and grams. SI units make pathology consistent across labs and countries.
The United States is the major holdout and reports most results in conventional units - based on weight per decilitre (mg/dL, g/dL, ng/mL). Both measure the same molecule, just in different ways.
This is why a healthy fasting glucose looks like “5.0” in Australia and “90” on an American forum - same person, same blood, two units. Most online health content uses American units, which makes Australian results look terrifying until you convert.
The Complete Unit Conversion Table
The 20 most-tested markers in Australia, with how the US reports the same thing and how to convert between them.
| Marker | Australia (SI) | US (Conv.) | Convert |
|---|---|---|---|
| Glucose | mmol/L | mg/dL | mg/dL = mmol/L x 18 5.0 mmol/L AU = 90 mg/dL US |
| Total Cholesterol | mmol/L | mg/dL | mg/dL = mmol/L x 38.67 5.2 mmol/L AU = 200 mg/dL US |
| LDL / HDL / Triglycerides | mmol/L | mg/dL | cholesterol x 38.67, TG x 88.6 TG uses a different multiplier than cholesterol |
| HbA1c | % AND mmol/mol | % only | mmol/mol = (% - 2.15) x 10.929 5.7% = 39 mmol/mol, 6.5% = 48 mmol/mol |
| Haemoglobin | g/L | g/dL | g/dL = g/L / 10 140 g/L AU = 14.0 g/dL US |
| Creatinine | umol/L | mg/dL | mg/dL = umol/L / 88.4 88 umol/L AU = 1.0 mg/dL US |
| Urea / BUN | mmol/L (urea) | mg/dL (BUN) | BUN = urea x 2.8 Australia reports urea, US reports BUN (a different number!) |
| Bilirubin | umol/L | mg/dL | mg/dL = umol/L / 17.1 17 umol/L AU = 1.0 mg/dL US |
| Vitamin D (25-OH) | nmol/L | ng/mL | ng/mL = nmol/L / 2.5 75 nmol/L AU = 30 ng/mL US |
| Vitamin B12 | pmol/L | pg/mL | pg/mL = pmol/L / 0.7378 200 pmol/L AU = 271 pg/mL US |
| Folate | nmol/L | ng/mL | ng/mL = nmol/L / 2.265 7 nmol/L AU = 3.1 ng/mL US |
| Ferritin | ug/L | ng/mL | 1:1 (same number) ug/L and ng/mL are numerically identical |
| TSH | mIU/L | uIU/mL | 1:1 (same number) Universal unit |
| Free T4 | pmol/L | ng/dL | ng/dL = pmol/L / 12.87 15 pmol/L AU = 1.17 ng/dL US |
| Calcium | mmol/L | mg/dL | mg/dL = mmol/L x 4.008 2.4 mmol/L AU = 9.6 mg/dL US |
| PSA | ng/mL or ug/L | ng/mL | 1:1 ug/L and ng/mL are identical |
| Iron | umol/L | ug/dL | ug/dL = umol/L x 5.587 20 umol/L AU = 112 ug/dL US |
| Albumin | g/L | g/dL | g/dL = g/L / 10 40 g/L AU = 4.0 g/dL US |
| White Cells / Platelets | x10^9/L | x10^3/uL or cells/uL | 1:1 (when units expressed as thousands) 5.0 x10^9/L = 5,000 cells/uL |
| eGFR | mL/min/1.73m^2 | mL/min/1.73m^2 | Universal Same units worldwide |
The Most Confusing Conversions
Vitamin D: nmol/L vs ng/mL
A 2.5x difference. 50 nmol/L (AU) is 20 ng/mL (US). Most American websites say “30 ng/mL is the minimum” - that is 75 nmol/L in AU.
HbA1c: % vs mmol/mol
Australia and the UK use both. Diabetes diagnosis cutoff is 6.5% OR 48 mmol/mol. They are the same thing reported two ways.
Cholesterol: mmol/L vs mg/dL
Total cholesterol target of 5.2 mmol/L is the same as 200 mg/dL. Multiply by ~38.7 to convert AU to US.
Urea (AU) vs BUN (US)
AU reports urea, the US reports Blood Urea Nitrogen (BUN). These are DIFFERENT numbers - the US value is about 2.8x the AU urea number.
Glucose: mmol/L vs mg/dL
Fasting target under 5.5 mmol/L = under 100 mg/dL. The 18x multiplier is easy to remember.
Creatinine: umol/L vs mg/dL
Healthy women run 60-90 umol/L (0.7-1.0 mg/dL), men 70-110 umol/L (0.8-1.2 mg/dL). Divide AU by ~88 for the US number.
Why Some Units Are Universal
A handful of measurements use the same units everywhere. Cell counts (x10^9/L), ferritin (ug/L = ng/mL), PSA (ng/mL = ug/L), TSH (mIU/L = uIU/mL) and eGFR (mL/min/1.73m^2) read the same in any country.
That is because they are already expressed in proportional units rather than weight-per-volume. When you see those, you can compare across any reference source without conversion.
SmarterBlood Handles the Units For You
Upload any blood test (Australian or international) - SmarterBlood reads the units automatically and shows you whether each marker is in the right range for YOUR units.