Urea / BUN
Urea / Blood Urea Nitrogen
Urea is a waste product made when your body breaks down protein. Your kidneys remove it in urine. Some reports measure urea; others report blood urea nitrogen, or BUN, which measures the nitrogen part.
See your Urea / BUN in context.
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What does a high urea or BUN result mean?
A high result can reflect reduced kidney clearance, dehydration or increased protein breakdown. It is not specific enough to diagnose kidney disease by itself. A low result can also have several explanations, including lower protein intake.
Check which test and units your report uses
Urea and BUN describe related measurements but have different numerical values. There is no universal optimal number. Your clinician interprets the result with creatinine, eGFR, hydration and your health history.
Sources: MedlinePlus (NIH)
What can change this result?
What can raise it
- Dehydration, such as after vomiting, diarrhea or heavy sweating.
- Eating a lot of protein.
- Reduced kidney filtering or bleeding in the digestive tract.
What can make it lower
- Eating very little protein or being undernourished.
- Liver problems that reduce urea production.
A lower BUN is not a goal on its own. Discuss recent illness, usual protein intake and your creatinine or eGFR result together.
What should I do next?
- Check whether your report says urea or BUN, and keep the units with the number.
- Review creatinine and eGFR from the same blood sample.
- Tell your clinician about vomiting, diarrhea, recent illness or changes in diet and medicines.
How this test works
Your liver converts nitrogen from protein breakdown into urea. A BUN test reports only the nitrogen within that urea. This is why the two measurements cannot be compared directly without the correct conversion.