Test Detail
Interpreting Results

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Written by
Dr. Shreya Gupta
BDS, MDS - Oral and Maxillofacial Pathology
Reviewed by
Dr. Lalit Mohan Gupta
MBBS, MD - Microbiology
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What is Urea?

Urea is a metabolic by-product of the process of conversion of protein into amino acids. Urea is formed in the liver and is transported by blood to the kidneys where it is excreted with urine. The Urea Test or Blood Urea Nitrogen (BUN) Test measures the levels of urea in the blood.

Why is Urea done?

The BUN Test is performed:

    ·         As a part of metabolic panel tests for regular health checkups

    ·         To check the functioning of the kidneys

    ·         To diagnose kidney diseases

    ·         To monitor efficacy of treatments for kidney diseases like dialysis

What does Urea Measure?

Urea is a by-product of protein metabolism. Proteins consumed in the diet are digested and converted into amino acids, which are utilized by the body. This metabolic process creates ammonia as a by-product. Ammonia is toxic and is thus rapidly converted by the liver to form the much less toxic compound urea that is transported relatively safely in blood. Urea formed in the liver is transported by the blood to the kidneys where it is filtered out of the blood and excreted out of the body in a solution called urine. The body continuously produces and excretes urea, hence a low and steady level of urea is continuously maintained in blood.

BUN levels in the blood are affected due to impairment of kidney function, or due to large-scale liver conditions. Primarily, BUN Test results are used to evaluate kidney functioning. Results are often interpreted together with results of Creatinine Test that measures the levels of another metabolic waste, creatinine, which is also excreted through urine.

Interpreting Urea results


Normal range (Approx.):



    0-1 week


    1 week to 1 year


    1-12 years


    12-60 years


    60-90 years


    >90 years


    Higher than normal BUN levels indicate impaired kidney function such that the kidneys are unable to effectively filter waste products out of the blood.

    Lower than normal BUN levels are usually clinically insignificant. However, lower levels may be associated with large-scale liver conditions in some cases.

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

Frequently Asked Questions about Urea

Q. How is this test performed?
This test is performed on a blood sample. A syringe with a fine needle is used to withdraw blood from a blood vessel in your arm. The healthcare provider will tie an elastic band around your arm to make the blood vessels swell with blood. This makes it easier to withdraw blood. You may be asked to tightly clench your fist. Once the veins are clearly visible, the area is cleaned with an antiseptic solution and then the needle is inserted into the blood vessel to collect the sample. You will feel a tiny pinprick during the procedure. Blood sample once collected will then be sent to the laboratory.
Q. Is there any preparation required before the Blood Urea Nitrogen test?
Inform the doctor about any medications you may be taking as certain medications like carbamazepine, methotrexate, rifampin, etc. can falsely elevate BUN levels. No other preparations are required unless specified by your doctor.
Q. Is there any risk associated with the Blood Urea Nitrogen Test?
There is no risk associated with the test. However, since this test involves a needle prick to withdraw the blood sample, in rare cases, a patient may experience excessive bleeding, hematoma formation (blood collection under the skin), bruising or infection at the site of needle prick.
Q. What other tests can be prescribed by your doctor in case the results of Blood Urea Nitrogen Test is not normal?
Other tests that may be prescribed upon appearance of an abnormal result in the Blood Urea Nitrogen Test include: · Kidney Function Tests · Blood Creatinine Test · Glomerular Filtration Rate · Blood Sugar Tests · Lipid Profile Test · Imaging Tests
Q. What factors can give rise to high BUN levels?
High levels of Blood Urea Nitrogen may occur due to: · Heart diseases · Congestive heart failure · Recent heart attack · Bleeding in gastrointestinal tract · Dehydration · Severe burns · High levels of dietary protein · Kidney diseases · Renal failure · Urinary tract obstruction · Stress · Shock
Q. What factors can give rise to a low BUN levels?
Low levels of Blood Urea Nitrogen may occur due to: · Severe liver damage or liver failure · Malnutrition · Severe protein deficiency · Drinking excessive water or excess fluids inserted through IV (intravenous)
Q. What are the common symptoms of kidney disease that may necessitate BUN Test?
The BUN Test may be performed to evaluate kidney functioning upon appearance of kidney disorder symptoms, including: · Need to urinate more often · Low urine volume · Difficulty during urination or painful urination · Foamy, bloody, or dark colored urine · Poor appetite · Itching · Fatigue and weakness · Swelling (edema), especially in the lower limbs, around the eyes, and face · Muscle cramps · Sleeping difficulty · Pain in the mid back region just below the rib cage (location of kidneys) · Hypertension (high blood pressure)
Q. What can produce false results in the BUN Test?
False results can appear in the BUN Test due to a number of factors, including: · Protein rich diet · Use of steroid · Dehydration · Burn injury · Aging · Certain medications like carbamazepine, methotrexate, rifampin, etc. · Pregnancy
Q. What is BUN to Creatinine Ratio?
Since false results can appear easily in the BUN test, blood creatinine test is performed to measure creatinine levels in the blood. The results of both these tests are interpreted together and expressed as a ratio of BUN to Creatinine, the normal range of which lies between 10:1 and 20:1. The BUN:Creatinine ratio serves as a better indication of kidney function than BUN values by themselves. The ratio also helps in the identification of conditions affecting kidney function but not directly related to kidney disorders, like congestive heart failure, bleeding in the gastrointestinal tract, etc.
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