Why do US and international labs use different units?

US labs report most chemistry in mass-per-volume 'conventional' units (mg/dL, ng/mL). Most other countries and the research literature use SI molar units (mmol/L, nmol/L), which count molecules rather than mass. The conversion factor is fixed for each analyte because it comes from its molecular weight.

How do I convert hemoglobin A1c from % to mmol/mol?

A1c isn't a unit swap — the two scales are different standardizations. Use the NGSP/IFCC master equation: mmol/mol = (A1c% − 2.15) × 10.929. So 5.7% ≈ 39 mmol/mol and 6.5% ≈ 48 mmol/mol. The tool also shows estimated average glucose (eAG = 28.7 × A1c − 46.7 mg/dL).

Does converting units change whether my result is normal?

No. The value and the reference range convert by the same factor, so a result inside the range in mg/dL is inside the equivalent range in mmol/L. Just make sure you compare against a range expressed in the same unit.

Why is Lp(a) missing?

Lipoprotein(a) mass (mg/dL) and particle number (nmol/L) don't have a fixed conversion — the ratio depends on the size of the apo(a) isoform and varies between people. Guidelines now recommend reporting Lp(a) in nmol/L, so compare like with like rather than converting.

Free tool

Lab Test Unit Converter

The short answer

Choose the analyte, type your value, and the converter switches between US conventional units and SI units using the standard published factors — for example glucose mg/dL × 0.0555 = mmol/L, and total testosterone ng/dL × 0.0347 = nmol/L. Hemoglobin A1c uses the NGSP-to-IFCC master equation instead of a simple multiplier.

Analytes: 30
Directions: US ↔ SI
Method: Published factors
Cost: Free

AnalyteValue in mg/dL

Result

5.55 mmol/L

100 mg/dL × 0.0555

See the Glucose reference range →

What are the conversion factors for common blood tests?

Multiply the US conventional value by the factor to get the SI value; divide to go back. Factors are fixed per analyte because they derive from molecular weight.

Analyte	US unit	SI unit	× factor	Note
Glucose	mg/dL	mmol/L	0.0555
Total cholesterol	mg/dL	mmol/L	0.02586
LDL cholesterol	mg/dL	mmol/L	0.02586
HDL cholesterol	mg/dL	mmol/L	0.02586
Triglycerides	mg/dL	mmol/L	0.01129
Testosterone (total)	ng/dL	nmol/L	0.03467
Free testosterone	pg/mL	pmol/L	3.467	1 pg/mL = 0.1 ng/dL
Estradiol	pg/mL	pmol/L	3.671
Progesterone	ng/mL	nmol/L	3.18
Prolactin	ng/mL	mIU/L	21.2	WHO 3rd international standard
Cortisol	µg/dL	nmol/L	27.59
DHEA-S	µg/dL	µmol/L	0.02714
Vitamin D, 25-hydroxy	ng/mL	nmol/L	2.496
Vitamin B12	pg/mL	pmol/L	0.7378
Folate	ng/mL	nmol/L	2.266
Ferritin	ng/mL	µg/L	1	Same number, different label
Iron	µg/dL	µmol/L	0.179
Creatinine	mg/dL	µmol/L	88.42
BUN (urea nitrogen)	mg/dL	mmol/L	0.357	Converts to urea in mmol/L
Uric acid	mg/dL	µmol/L	59.48
Calcium	mg/dL	mmol/L	0.2495
Magnesium	mg/dL	mmol/L	0.4114
Phosphorus	mg/dL	mmol/L	0.3229
Bilirubin (total)	mg/dL	µmol/L	17.1
Albumin	g/dL	g/L	10
Hemoglobin	g/dL	g/L	10
Insulin	µIU/mL	pmol/L	6.945
TSH	µIU/mL	mIU/L	1	Same number, different label
PSA	ng/mL	µg/L	1	Same number, different label
C-reactive protein	mg/L	mg/dL	0.1
Hemoglobin A1c	% (NGSP)	mmol/mol (IFCC)	(A1c − 2.15) × 10.929	eAG (mg/dL) = 28.7 × A1c − 46.7

How do you convert glucose, cholesterol and testosterone by hand?

Glucose

100 mg/dL × 0.0555 = 5.6 mmol/L. The prediabetes fasting band of 100–125 mg/dL is 5.6–6.9 mmol/L.

Cholesterol

LDL 100 mg/dL × 0.02586 = 2.6 mmol/L; 70 mg/dL — a common high-risk target — is 1.8 mmol/L.

Testosterone

300 ng/dL × 0.03467 = 10.4 nmol/L. European labs often quote a 12 nmol/L threshold, which is about 346 ng/dL.

Frequently asked questions

Which biomarkers does this tool cover?

Which tests give you these numbers?

Physician-authorized, drawn at Quest, Labcorp or BioReference. Results in 1–3 business days for most tests.