Test Detail
Interpreting Results

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Written by
Dr. Betina Chandolia
BDS, MDS - Oral Pathology and Microbiology
Reviewed by
Dr. Ashish Ranjan
MBBS, MD (Pharmacology)
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Blood Urea Nitrogen

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This test is for
Male, Female
Test Preparation
  1. No special preparation required


What is BUN?

Blood urea nitrogen (BUN) test measures the amount of urea nitrogen in your blood. Liver breaks down the proteins in your food and creates BUN and the kidneys get rid of this excess nitrogen by flushing it out of the body through urine. BUN is majorly an indicator of kidney or liver health.
The BUN test is advised if one experiences symptoms suggestive of kidney disease including painful urination, bloody or foamy urine, tiredness and more. It is also suggested to patients who are undergoing treatment for kidney disease.
Higher than normal BUN levels may also indicate dehydration, a high-protein diet, medications, burns, or other conditions. Sometimes BUN levels are likely to get affected by dietary conditions unrelated to kidney function.

Why is BUN done?

The Blood Urea Nitrogen test is done:

    • As a part of the routine comprehensive check-up

    • As a part of the basic metabolic panel

    • In case of signs and symptoms of kidney disease

    • In case a patient is undergoing treatment for kidney disease

What does BUN Measure?

The Blood Urea Nitrogen test measures the amount of urea nitrogen in the blood. Urea is a waste product which is formed in the liver. It is formed when protein is metabolized into amino acids. This leads to the production of ammonia which is further converted into urea which is a less toxic waste product. 

Both ammonia and urea have nitrogen as their component. The liver releases urea into the blood which is then carried out to the kidneys. Here, it is filtered out of the blood and then released into the urine. Since this is a continuous process, a small and stable amount of urea nitrogen always remains in the blood.

In the case of kidney or liver diseases, there is a change in the amount of urea present in the blood. If the liver produces urea in increased amounts or if there is any problem in the functioning of the kidneys, there can be difficulty in filtering out wastes of the blood which will lead to rising in urea concentrations in the blood. If due to liver damage or disease there is less production of urea, the concentration of BUN will fall.

The BUN test is done along with creatinine test to evaluate kidney function to diagnose kidney disease and to monitor patients undergoing treatment of kidney disease. 

Interpreting BUN results


The reference range for BUN is as follows:


Reference range in mg/dL

0 - 1 week

3 - 25

1 week - 1 year

4- 19

1 - 12 years

5 - 18

12 - 60 years

6 - 20

60 - 90 years

8- 23

> 90 years

10 - 31

Reference range may vary from lab to lab*

Answers to Patient Concerns & Frequently Asked Questions (FAQs) about BUN

Frequently Asked Questions about Blood Urea Nitrogen

Q. Is there any preparation required before the test?
Inform the doctor about the medications you may be taking. No other specific preparations are usually required before this test.
Q. How is the blood sample taken?
The healthcare provider takes a blood sample from the arm. The site from where the blood is to be withdrawn is cleaned with a swab of rubbing alcohol. This is then followed by inserting a small needle which has a tube attached to it for collecting blood. Once the sufficient blood for analysis is withdrawn, the needle is removed. The site is then covered with a gauze pad.
Q. Is there any risk associated with the withdrawal of blood sample procedure?
As such there is no risk but in few cases, bruising, bleeding, and infection at the puncture site can be seen. In very few cases, there can be swelling of the vein after the blood is withdrawn.
Q. What other tests can be advised by the doctor along with BUN test?
The BUN test is advised along with a creatinine test or renal panel in case a doctor suspects kidney diseases in the patient.
Q. What are the signs and symptoms of kidney dysfunction?
The signs and symptoms of kidney dysfunction include swelling around eyes or in the face, wrists, abdomen, thighs or ankles, fatigue, lack of concentration, poor appetite, and difficulty sleeping. Ther other symptoms can be foamy or bloody or coffee-colored urine, decrease in the amount of urine, discomfort in urinating (e.g., feeling of burning sensation while urinating or passage of discharge while urinating), change in frequency of urination, mid back pain below the ribs, and high blood pressure.
Q. What do abnormal results of BUN mean?
The increased levels of BUN are seen in case of impaired kidney function which may be due to acute or chronic kidney disease, damage or failure, and conditions causing obstruction of urine flow and dehydration. Along with that, levels of BUN can increase when there is decreased blood flow to the kidneys such as in case of congestive heart failure, shock, stress, recent heart attack or severe burns. The levels of BUN also rise when there is more than normal breakdown of protein, increase in protein diet or gastrointestinal bleeding. The decreased levels of BUN are seen in case of severe liver disease, malnutrition, and over hydration.
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