Urea Nitrogen (BUN)
Urea Nitrogen (commonly reported as BUN, Blood Urea Nitrogen) measures the nitrogen content of urea in the blood. It is the same urea cycle waste product as serum urea, just reported as the nitrogen fraction rather than the whole molecule (BUN ≈ Urea ÷ 2.14).
Why it matters: BUN is interchangeable with urea for kidney-function tracking, and the BUN/Creatinine ratio is a common way to distinguish dehydration or GI bleeding (high ratio) from intrinsic kidney issues (normal ratio).
May increase with:
May decrease with:
What is Urea Nitrogen (BUN)?
Urea Nitrogen (commonly reported as BUN, Blood Urea Nitrogen) measures the nitrogen content of urea in the blood. It is the same urea cycle waste product as serum urea, just reported as the nitrogen fraction rather than the whole molecule (BUN ≈ Urea ÷ 2.14).
What might a high or low Urea Nitrogen (BUN) mean?
BUN is interchangeable with urea for kidney-function tracking, and the BUN/Creatinine ratio is a common way to distinguish dehydration or GI bleeding (high ratio) from intrinsic kidney issues (normal ratio).
What is the typical reference range for Urea Nitrogen (BUN)?
The general-population reference range shown here is 2.1 – 7.1 mmol/L. Reference ranges describe the general population and are not a personal target — discuss your results with your physician.
What can affect Urea Nitrogen (BUN)?
It may be higher with: Kidney issues, Dehydration, High protein intake, GI bleeding, Heart failure. It may be lower with: Low protein diet, Liver issues, Overhydration, Pregnancy.
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