Kidney · Blood test
BUN (blood urea nitrogen): normal range explained
Also printed as: Blood Urea Nitrogen, Urea Nitrogen, B.U.N.
BUN, or blood urea nitrogen, measures the nitrogen carried in urea, the waste product your body makes when it breaks down protein and your kidneys clear from the blood. The adult range commonly printed is 7–20 mg/dL, within the 6 to 20 that MedlinePlus prints, but the range printed on your own report is the one that applies.
Last updated 4 sources
What is the normal range for BUN?
| Printed for | Range |
|---|---|
| Adults | 7–20mg/dL |
Reference ranges vary between laboratories. Always use the range printed on your own report. Why ranges differ between labs
Sources:MedlinePlus
What does BUN measure?
A BUN test measures the amount of urea nitrogen in your blood. Urea nitrogen is a waste product that forms as the body breaks down proteins; it travels in the blood to the kidneys, which remove it in urine. Lab Tests Online UK lists BUN as another name for its urea test; that a urea value sits on a different scale, because BUN counts only the nitrogen in urea, is Amara's own note rather than either page's.
Why do doctors order the BUN test?
Doctors order BUN to check how well the kidneys are working, usually with creatinine, as part of a routine check-up, a kidney function test or a metabolic panel. MedlinePlus lists screening for people at higher risk, including those with diabetes, high blood pressure, heart disease or a family history of kidney problems, and following treatment for kidney disease. Testing.com explains that BUN read with creatinine says more than BUN alone, which is why many reports print the BUN-to-creatinine ratio.
Sources:MedlinePlus, Testing.com
What can change your BUN result?
BUN moves with protein, fluids, age and the liver, so a single value needs context.
- A high-protein diet pushes BUN up, and a very low-protein diet pulls it down.
- Dehydration raises BUN without raising creatinine much, which skews the BUN-to-creatinine ratio high.
- BUN usually rises with age and varies by sex.
- Liver disease lowers BUN even when the kidneys are normal, because the liver makes less urea.
- Burns, a recent heart attack, bleeding in the gut and heart failure can raise it, which your doctor considers.
- Some medicines affect the result, and corticosteroids can raise the ratio. Tell your doctor everything you take, and do not stop a medicine without asking.
Sources:MedlinePlus, Testing.com
How do you read BUN on your lab report?
Reports print BUN in mg/dL, sometimes beside a urea line and often with a BUN-to-creatinine ratio, which Testing.com says is normally between 10 and 20 and is a plain number without units. Lab Tests Online UK lists BUN as another name for its urea test; a urea value is on a different scale, so read each against its own range.
MedlinePlus prints 6 to 20 mg/dL as the usual result and says normal values vary between labs. A BUN a little above the range after a day of little fluid or a protein-heavy meal can happen without any kidney change; your doctor reads it with creatinine, eGFR and your history rather than alone.
Amara reads BUN with the range printed beside it on each report, flags a value outside that range, and shows what changed since your last report. Try it with two sample reports
A sample Amara row for BUN: 23 mg/dL on 3 Mar 2026 at Lab A (sample), then 18 mg/dL on 21 Sep 2026 at Lab B (sample), each with its lab's printed range.
Questions people ask about BUN
What is BUN on a kidney function test?
BUN on a kidney function test stands for blood urea nitrogen, the amount of nitrogen carried in urea in your blood. MedlinePlus explains that urea nitrogen is a waste product from the breakdown of proteins which the kidneys remove, so it is used to check how well they are working. It is usually read with creatinine from the same sample.
What is the BUN to creatinine ratio?
The BUN-to-creatinine ratio divides your BUN by your creatinine, and Testing.com says a normal ratio falls between 10 and 20, reported as a plain number. Dehydration raises BUN more than creatinine, which pushes the ratio up, while liver disease lowers BUN and pulls it down. Your doctor uses the ratio with both values and your history.
Is BUN the same as urea?
BUN and urea describe the same waste product but are not the same number. Lab Tests Online UK lists BUN as another name for the urea test; Amara's own note is that BUN counts only the nitrogen in urea, while a urea test counts the whole molecule. If your report prints both lines, read each against its own printed range.
What can make BUN high without kidney disease?
BUN can rise without any kidney disease. MedlinePlus lists dehydration, a high-protein diet, burns, a recent heart attack and certain medicines as causes, and Testing.com says dehydration raises BUN more than creatinine. Age pushes it up a little too. A doctor reads a high BUN with creatinine, eGFR and your history before drawing any conclusion.
Sources
- BUN (Blood Urea Nitrogen)MedlinePlus · medlineplus.gov · Opened
- BUN - blood testMedlinePlus · medlineplus.gov · Opened
- BUN/Creatinine Ratio TestTesting.com · testing.com · Opened
- Urea TestLab Tests Online UK · labtestsonline.org.uk · Opened
About this page
Every statement on this page comes from the sources listed above. Ranges are those commonly printed on Indian lab reports; the range printed on your own report is the one that applies.
Published by Amara Health, a product of MetaNova AI Private Limited, Hyderabad.
Amara Health does not provide medical advice, diagnosis or treatment. Information shown by Amara is based on available health records and may contain errors. Review important information against the original report and consult a qualified healthcare professional for medical decisions. Do not use Amara for medical emergencies.
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