What Does It Mean When Your BUN-to-Creatinine Ratio Is High?

A higher-than-normal ratio of blood urea nitrogen to creatinine may indicate congestive heart failure, a urinary tract obstruction, gastrointestinal bleeding or trauma, according to Quest Diagnostics. The test attempts to ascertain whether someone has some kind of kidney problem such as acute or chronic renal disease.

An increased BUN to creatinine ratio could reveal dehydration or higher levels of protein in a patient's diet, notes the American Association for Clinical Chemistry. A higher ratio occurs when less blood reaches the kidneys. A normal BUN to creatinine ratio lies between 10-to1 and 20-to-1. The BUN to creatinine ratio may decrease with liver disease or malnutrition. Both substances indicate how well the kidneys filter waste products from the body. Levels of blood urea nitrogen generally increase with age.

Creatinine clearance tests determine how much of the chemical gets removed from a patient's body through the kidneys, says MedicineNet. Higher creatinine levels may mean there is a problem with kidney filtration. Doctors compare creatinine levels in both blood and urine over a 24-hour period to ascertain kidney function. The normal range of creatinine clearance goes from 88 to 128 milliliters per minute in females and 97 to 137 milliliters per minute with males. Urea, a byproduct of metabolism, can also build up in blood if someone has kidney problems. A BUN to creatinine ratio provides more precise data regarding kidney function than testing for both substances separately.