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BUN to Urea Converter (mg/dL to mmol/L)

Convert blood urea nitrogen (BUN, mg/dL) to urea in mmol/L or mg/dL and back: urea mmol/L = BUN × 0.357 and urea mg/dL = BUN × 2.14, with the usual adult reference range.

Value

The value is

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How it works

urea (mmol/L) = BUN (mg/dL) ÷ 2.8014 ≈ BUN × 0.357 · urea (mg/dL) = BUN (mg/dL) × 2.144 · urea (mg/dL) = urea (mmol/L) × 6.006 · BUN (mg/dL) = urea (mmol/L) × 2.8

BUN (blood urea nitrogen) reports only the nitrogen in urea. Each urea molecule (60.06 g/mol) contains two nitrogen atoms (28.01 g/mol), so urea weighs 2.14 times its nitrogen: urea in mg/dL = BUN × 2.14. One millimole of urea contains 28.01 mg of nitrogen, so urea in mmol/L = BUN in mg/dL ÷ 2.8 (× 0.357). In mmol/L, urea and urea nitrogen are the same number. The United States reports BUN, the UK and Australia report urea in mmol/L, and Spain and much of Latin America report urea in mg/dL.

Worked example

A BUN of 14 mg/dL ÷ 2.8014 = 5.0 mmol/L of urea, and 14 × 2.144 = 30.0 mg/dL of urea. A Spanish lab report showing urea 40 mg/dL corresponds to a BUN of 40 ÷ 2.144 = 18.7 mg/dL.

Sources: MedlinePlus: BUN (blood urea nitrogen) test · Higgins C. Urea and the clinical value of measuring blood urea concentration. acutecaretesting.org

Frequently asked questions

How do I convert BUN to urea?

For urea in mmol/L multiply BUN (mg/dL) by 0.357; for urea in mg/dL multiply BUN by 2.14. A BUN of 20 mg/dL is 7.1 mmol/L or 42.8 mg/dL of urea.

How do I convert urea to BUN?

Divide urea in mg/dL by 2.14, or multiply urea in mmol/L by 2.8. Urea 50 mg/dL = BUN 23.3 mg/dL; urea 8 mmol/L = BUN 22.4 mg/dL.

Are BUN and urea the same test?

They measure the same substance but report it differently: BUN counts only the nitrogen part of the urea molecule, urea reports the whole molecule. Always check which one your report shows before comparing with a reference range.

What is a normal BUN?

About 6–20 mg/dL in adults (MedlinePlus), which is 2.1–7.1 mmol/L or 13–43 mg/dL of urea. Values rise with dehydration, high protein intake, gastrointestinal bleeding and kidney disease.

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Educational calculation only, not medical advice or a diagnosis. Reference ranges and units differ between laboratories; interpret any result with your doctor in the context of your full clinical picture.