The term for blood urea nitrogen, or BUN, and creatinine levels in the body is BUN-to-creatinine ratio, states WebMD. A high BUN-to-creatinine ratio indicates potential issues such as kidney disease, heart failure, dehydration or bleeding in the gastrointestinal tract.
The amount of nitrogen in the blood is a result of waste from urea, which is made when the body breaks down protein, explains WebMD. Sometimes the kidneys cannot properly remove nitrogen from the blood, and this causes high BUN levels. A creatinine test is done along with the BUN test to check for high creatinine levels. Creatinine levels in the blood are also related to kidney function. It is important to note that some medications and a diet high in protein also cause a high BUN level.