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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.
A health professional uses a needle to take a blood sample, usually from the arm.
When a blood sample is taken, you may feel nothing at all from the needle. Or you might feel a quick sting or pinch.
There is very little chance of having a problem from this test. When a blood sample is taken, a small bruise may form at the site.
Each lab has a different range for what's normal. Your lab report should show the range that your lab uses for each test. The normal range is just a guide. Your doctor will also look at your results based on your age, health, and other factors. A value that isn't in the normal range may still be normal for you.
Adaptation Date: 7/6/2021
Adapted By: Alberta Health Services
Adaptation Reviewed By: Alberta Health Services
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