Blood urea nitrogen (BUN) test
Quick answer: A BUN test measures urea nitrogen, a waste product that the kidneys remove from the blood. It is part of routine kidney checks and is often done with creatinine.
- SampleBlood
- TakesAbout 5 minutes
- Before the testNo special preparation is usually needed.
How the test is done
- 1You sit and the skin on your arm is cleaned
- 2A needle draws blood into a tube
- 3The lab measures urea nitrogen, often with creatinine
- 4Your doctor compares BUN with creatinine to understand kidney function
What your results can mean
Reading your report
Normal ranges differ between labs and by age and sex, so discuss your result with your doctor.
If the result is outside the usual range
A high level can be seen with kidney problems, dehydration, a high-protein diet, bleeding in the stomach or some medicines. A low level can be seen with liver disease or poor protein intake.
Who usually has this test
People having routine health checks, and people with kidney disease, high blood pressure, diabetes or dehydration.
Risks and aftercare
Any bruise at the needle site usually fades within a few days.
Names and options
Also called: BUN, urea nitrogen
Listed by the hospital as
- BLOOD UREA NITROGEN
Questions about this test
Is BUN the same as urea?
They measure the same waste product in different ways. BUN measures only the nitrogen part of urea, so the numbers differ, but they give the same information.
Can dehydration raise BUN?
Yes. When you are dehydrated, BUN can rise even if your kidneys are healthy. Drinking fluids normally before the test helps.
What is the BUN to creatinine ratio?
Comparing the two helps doctors tell whether a raised BUN is from the kidneys or from causes such as dehydration or bleeding.
Related tests
Tamara Hospital & IVF Centre, Rajajinagar
34/3, 10th Cross Road, opp. Vardhaka Sardar Patel School, 1st N Block, 2nd Stage, Rajajinagar, Bengaluru 560010
The hospital is open 24 hours. Call before you come to check the timing for your scan or sample collection.
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This page explains each test in general terms so you know what to expect. It is not medical advice: your doctor decides which tests you need and what your results mean. Reference ranges differ between laboratories. Updated 4 November 2026.