Elevated blood urea nitrogen and creatinine levels usually indicate the kidneys are not functioning as well as they should, explains Riverside Health System. The kidneys are responsible for removing BUN and creatinine from the bloodstream.
A normal BUN result ranges from 6 to 20 milligrams per deciliter, reports MedlinePlus. Urinary obstructions, kidney disease, dehydration, congestive heart failure and heart attack can cause elevated BUN levels. A normal creatinine result ranges from 0.7 to 1.3 milligrams per deciliter in men and 0.6 to 1.1 milligrams per deciliter in women. Kidney disease, dehydration and urinary blockages can also cause elevated creatinine levels.