Women and children may have lower BUN levels than men because of how their bodies break down protein.Drinking too much liquid may cause overhydration and cause a low BUN value.A low BUN value may be caused by a diet very low in protein, by malnutrition, or by severe liver damage.A very high BUN-to-creatinine ratio may be caused by bleeding in the digestive tract or respiratory tract.

High BUN-to-creatinine ratios occur with sudden (acute) kidney problems, which may be caused by shock or severe dehydration.A high BUN value may be caused by a high-protein diet, Addison's disease, or tissue damage (such as from severe burns), or from bleeding in the gastrointestinal tract. The American Board for Internal Medicine lists the typical reference range for blood urea nitrogen as 7 to 20 mg/dL.Be sure to tell your doctor about all the non-prescription and prescription medicines you take. High BUN levels can also be caused by low blood flow to the kidneys caused by dehydration or heart failure. Kidney damage can be caused by diabetes or high blood pressure that directly affects the kidneys. A high BUN value can mean kidney injury or disease is present.A value that isn't in the normal range may still be normal for you. A higher than normal BUN level may be a sign that your kidneys are not working well. In general, about 7 - 20 mg/dL is a normal level. What is considered a normal BUN level depends on your age and other health conditions you may have. Your doctor will also look at your results based on your age, health, and other factors. BUN test results are measured in milligrams per deciliter (mg/dL). Your lab report should show the range that your lab uses for each test. A BUN-to-creatinine ratio can help your doctor check for problems, such as dehydration, that may cause abnormal BUN and creatinine levels.Įach lab has a different range for what's normal. Blood urea nitrogen (BUN) and creatinine tests can be used together to find the BUN-to-creatinine ratio (BUN:creatinine). 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. Blood urea nitrogen to creatinine ratio (BUN:creatinine)Ī BUN test may be done with a blood creatinine test. A low BUN level can occur normally in the second or third trimester of pregnancy. Liver disease or damage can lower your BUN level. Heart failure, dehydration, or a diet high in protein can also make your BUN level higher. If your kidneys are not able to remove urea from the blood normally, your BUN level rises. Urea is made in the liver and passed out of your body in the urine.Ī BUN test is done to see how well your kidneys are working. Urea is made when protein is broken down in your body. A blood urea nitrogen (BUN) test measures the amount of nitrogen in your blood that comes from the waste product urea.

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