What Is the BUN-to-Creatinine Ratio Used to Measure?

Doctors use blood urea nitrogen to creatinine ratio to determine the working condition of the kidneys, as WebMD explains. A BUN test helps to determine the amount of nitrogen excreted from the blood through urea, while a blood creatinine test measures the level of creatinine. Doctors also use the BUN-to-creatinine ratio test to check for possible problems such as dehydration that may alter normal levels of BUN and creatinine.

Dehydration leads to high BUN levels, which in effect raises the BUN-to-creatinine ratio, notes WebMD. High levels of both the BUN and creatinine could be an indication of kidney disease or obstruction of urine flow from the kidneys. Consequently, doctors use these tests to check if the kidneys work normally, evaluate the progress of kidney disease and assess the effectiveness of kidney disease treatment.

A BUN-to-creatinine ratio test is more precise than a creatinine clearance test, which measures the glomerular filtration rate of the kidneys, according to MedicineNet. The ratio provides information on both the kidney function and the possible underlying cause of any abnormality. For instance, doctors associate high levels of creatinine in infants with bacteremia. A high level of the metabolic waste product in adults suggests a high risk of prostate cancer.