Kidney function test: What do elevated creatinine and BUN indicate?

Recent kidney function tests revealed that I have elevated creatinine and BUN levels. What does this mean?

- Sandy / Florida

Mayo Clinic urologist Erik Castle, M.D., and colleagues answer select questions from readers.

Answer

Elevated creatinine and blood urea nitrogen (BUN) levels are likely evidence of decreased kidney function. Creatinine and urea nitrogen are waste products that your kidneys normally remove from your blood. If your kidneys are not working properly, these substances may build up in your blood. Kidney function tests include blood tests that measure creatinine and urea nitrogen.

If you have elevated creatinine and BUN, your doctor will likely recommend additional tests to further evaluate your kidney function. Tests may include:

Urine tests to look for increased protein, red blood cells and casts in your urine as indicators of impaired kidney function
Glomerular filtration rate to determine your kidney function as a percent of normal