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A blood urea nitrogen (BUN) or urea test measures the amount of nitrogen in your blood that comes from the waste product urea. Urea is made when protein is broken down in your body. Urea is made in the liver and passed out of your body in the urine.
A urea test is done to see how well your kidneys are working. If your kidneys are not able to remove urea from the blood normally, your urea level rises. Heart failure, dehydration, or a diet high in protein can also make your urea level higher. Liver disease or damage can lower your urea level. A low urea level can occur normally in the second or third trimester of pregnancy.
A urea test may be done with a blood creatinine test. The level of creatinine in your blood also tells how well your kidneys are working—a high creatinine level may mean your kidneys are not working properly. Urea and creatinine tests can be used together to find the urea-to-creatinine ratio (urea:creatinine). A urea-to-creatinine ratio can help your doctor check for problems, such as dehydration, that may cause abnormal urea and creatinine levels.
A urea test is done to:
Do not eat a lot of meat or other protein in the 24 hours before having a urea test.
The health professional drawing blood will:
The blood sample is taken from a vein in your arm. An elastic band is wrapped around your upper arm. It may feel tight. You may feel nothing at all from the needle, or you may feel a quick sting or pinch.
There is very little chance of a problem from having a blood sample taken from a vein.
A urea test measures the amount of nitrogen in your blood that comes from the waste product urea.
The normal values listed here—called a reference range—are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what's normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab.
10–20 milligrams per decilitre (mg/dL) or 3.6–7.1 millimoles per litre (mmol/L)
6–25 with 15.5 being the best value.
Reasons you may not be able to have the test or why the results may not be helpful include:
CitationsPagana KD, Pagana TJ (2010). Mosby's Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby Elsevier.Other Works ConsultedChernecky CC, Berger BJ (2008). Laboratory Tests and Diagnostic Procedures, 5th ed. St. Louis: Saunders.Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.Pagana KD, Pagana TJ (2010). Mosby's Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby Elsevier.
Adaptation Date: 5/5/2021
Adapted By: Alberta Health Services
Adaptation Reviewed By: Alberta Health Services
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