Urea Nitrogen (BUN) — mg/dL to mmol/L

In short To convert urea nitrogen from mg/dL to mmol/L, multiply by 0.356972 — so one mg/dL is 0.356972 mmol/L, and one mmol/L is 2.80134 mg/dL. 10 mg/dL BUN is 3.6 mmol/L urea; 20 mg/dL BUN is 7.1 mmol/L urea; 40 mg/dL BUN is 14.3 mmol/L urea. The factor comes from the molar mass, because the conversion counts the two nitrogen atoms in urea, 28.01 g/mol, not the whole urea molecule; that is why it differs for every analyte and why a single "lab unit converter" factor does not exist. This is not a unit conversion at all — it is a change of substance. American labs report the *nitrogen* in urea; almost everyone else reports *urea*. Urea contains two nitrogen atoms out of a molar mass of 60.06, so BUN in mg/dL converts to urea in mmol/L by 0.357, and anyone treating the two names as the same measurement in different units will be out by a factor of 2.14. This converts units. It does not interpret results, does not compare your value against a reference interval, and is not a substitute for the clinician who ordered the test — reference intervals differ between laboratories, methods and populations.