Why are blood test units different between countries?

The United States primarily uses conventional units (e.g., mg/dL), while most other countries adopted the SI (Systeme International) system in the 1970s, which uses units like mmol/L. The difference is historical — the US medical system retained the older measurement conventions while the rest of the world standardized to SI units for scientific consistency.

How do I convert mg/dL to mmol/L?

The conversion factor depends on the specific biomarker because each has a different molecular weight. For glucose, multiply mg/dL by 0.0555 to get mmol/L. For cholesterol, multiply mg/dL by 0.0259. Our converter handles 50+ biomarkers automatically so you don't need to memorize the factors.

Do all blood tests use different units internationally?

No. Some blood tests use the same units worldwide. For example, HbA1c is reported as a percentage globally, and TSH is measured in mIU/L (or µIU/mL, which is equivalent) in both systems. However, most chemistry and hormone tests have different conventional and SI units.

What is the difference between conventional and SI units?

Conventional units typically express concentrations as mass per volume (e.g., mg/dL, ng/mL), while SI units express concentrations as moles per volume (e.g., mmol/L, nmol/L). SI units are based on the molecular weight of the substance, providing a more scientifically standardized measurement.

Can incorrect unit conversion affect my health decisions?

Yes. Misinterpreting units can lead to significant errors. For example, a glucose reading of 100 mg/dL is normal, but 100 mmol/L would be dangerously high. Always verify which units your lab report uses before comparing results to reference ranges or international guidelines.

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How to Convert Blood Test Units

Blood test results can be reported in different measurement units depending on the country, laboratory, or healthcare system. The two main systems are conventional units (commonly used in the United States) and SI units (Système International, used in most other countries). This can make it confusing to compare results from different labs or understand values from international medical literature.

Why Do Different Countries Use Different Units?

The United States primarily uses conventional units such as mg/dL (milligrams per deciliter) and ng/dL (nanograms per deciliter). Most of Europe, Australia, Canada, and the rest of the world use SI units such as mmol/L (millimoles per liter) and nmol/L (nanomoles per liter). The SI system was adopted internationally in the 1970s to standardize scientific measurement, but the US medical system largely retained the older conventional system.

This means a glucose reading of 100 mg/dL in the US is the same as 5.55 mmol/L in Europe. Both values are identical — just expressed differently.

Common Blood Test Unit Conversions

Biomarker	Conventional Unit	SI Unit	Multiply by
Glucose	mg/dL	mmol/L	0.0555
Total Cholesterol	mg/dL	mmol/L	0.0259
LDL Cholesterol	mg/dL	mmol/L	0.0259
HDL Cholesterol	mg/dL	mmol/L	0.0259
Triglycerides	mg/dL	mmol/L	0.0113
Creatinine	mg/dL	µmol/L	88.4
Uric Acid	mg/dL	µmol/L	59.48
Bilirubin (Total)	mg/dL	µmol/L	17.1
Testosterone	ng/dL	nmol/L	0.0347
Vitamin D (25-OH)	ng/mL	nmol/L	2.496
Vitamin B12	pg/mL	pmol/L	0.7378
Iron	µg/dL	µmol/L	0.1791
Cortisol	µg/dL	nmol/L	27.59
Hemoglobin	g/dL	g/L	10

How Unit Conversion Works

Each biomarker has a specific conversion factor based on its molecular weight. To convert from conventional units to SI units, you multiply by the conversion factor. To convert back, you divide by it. For example:

Glucose: 100 mg/dL × 0.0555 = 5.55 mmol/L
Total Cholesterol: 200 mg/dL × 0.0259 = 5.18 mmol/L
Creatinine: 1.0 mg/dL × 88.4 = 88.4 µmol/L
Testosterone: 500 ng/dL × 0.0347 = 17.35 nmol/L

Tips for Comparing Blood Test Results

Always check the units printed on your lab report before comparing values with reference ranges or past results.
When comparing results from different labs or countries, convert to the same unit system first.
Some biomarkers (like HbA1c or TSH) use the same units worldwide, so no conversion is needed.
If in doubt, ask your healthcare provider to clarify which units your results are in.

Medicinsk ansvarsfriskrivning: Detta verktyg är endast avsett för informations- och utbildningsändamål. Det är inte ett substitut för professionell medicinsk rådgivning, diagnos eller behandling. Omvandlingsfaktorerna baseras på allmänt accepterade kliniska referenser men kan variera något mellan olika laboratorier. Rådgör alltid med din vårdgivare för tolkning av dina blodprovsresultat.

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