Blood urea nitrogen (BUN) and creatinine tests can be used together to find the BUN-to-creatinine ratio (BUN:creatinine). A BUN-to-creatinine ratio can help your doctor check for problems, such as dehydration, that may cause abnormal BUN and creatinine levels.
http://www.emedicinehealth.com/script/main/art.asp?articlekey=127119
However, even if your blood urea nitrogen levels are too low or too high, you may not necessarily have a kidney condition. Certain factors, such as dehydration, pregnancy, high or low protein intake, steroids, and aging can impact your levels without indicating a health risk. Advertisement.
http://www.healthline.com/health/blood-urea-nitrogen-test
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http://answers.webmd.com/answers/5002320/causes-of-low-bun-level
If your kidneys are not able to remove urea from the blood normally, your BUN level rises. Heart failure, dehydration, or a diet high in protein can also make your BUN level higher. Liver disease or damage can lower your BUN level. A low BUN level can occur normally in the second or third trimester of pregnancy.
http://www.emedicinehealth.com/script/main/art.asp?articlekey=127119
A blood urea nitrogen (BUN) test checks kidney function by measuring how much urea nitrogen is in your blood. Urea nitrogen is a waste product from the breakdown of protein in the body. Normally, this waste is filtered by the kidneys and leaves the body through urine.
http://www.healthline.com/health/blood-urea-nitrogen-test
Liver disease may be associated with near-normal values of both BUN (due to decreased urea production) and serum creatinine (due to muscle wasting), despite a significant decline in renal function manifested by decreased GFR.
http://emedicine.medscape.com/article/2073979-overview
A blood urea nitrogen (BUN) test is done to: 1  See if your kidneys are working normally. 2  See if your kidney disease is getting worse. 3  See if treatment of your kidney disease is working.  Check for severe dehydration. Dehydration generally causes BUN levels to rise more than creatinine levels.
http://www.emedicinehealth.com/script/main/art.asp?articlekey=127119
Urea is found dissolved in blood and is excreted by the renal tubules. In addition, a small amount of urea is also excreted in sweat. Therefore, the BUN level may reflect functioning of the liver and/or kidneys. The reference range of the BUN level is 3-20 mg/dL.
http://emedicine.medscape.com/article/2073979-overview
These important organs also control the pH, salt levels, and potassium levels in the body. The kidneys even produce hormones that manage red blood cell production and regulate blood pressure. A blood urea nitrogen (BUN) test is used to determine how well your kidneys are working. It does this by measuring the amount of urea nitrogen in the blood. Urea nitrogen is a waste product that’s created in the liver when the body breaks down proteins. Normally, the kidneys filter out this waste, and urinating removes it from the body. BUN levels tend to increase when the kidneys or liver are damaged.
http://www.healthline.com/health/bun
Urea nitrogen levels tend to increase with age. Infants have lower levels than other people do, and the range in children varies. Generally, a high blood urea nitrogen level means your kidneys aren't working well. But elevated blood urea nitrogen can also be due to: Urinary tract obstruction. Congestive heart failure or recent heart attack. Gastrointestinal bleeding. Dehydration, resulting from not drinking enough fluids or for other reasons.
http://www.mayoclinic.org/tests-procedures/blood-urea-nitrogen/details/results/rsc-20211280
what causes a decreased bun level
Liver disease causes a decreased Blood Urea Nitrogen level. A decreased BUN level is caused by liver disease.