by Angela Clem

Created on: July 16, 2008   Last Updated: August 16, 2010

If your cat has ever had blood tests, you will likely have seen results for Cre (or creatinine) and BUN. Creatinine is a waste product of protein metabolism produced by the body. It is filtered by the kidneys and excreted in the urine.

Creatinine levels are indicative of kidney function. In conjunction with blood urea nitrogen (BUN), creatinine levels are used to determine how well the kidneys are functioning. High levels of creatinine usually indicate that the kidneys are malfunctioning; however, some large, muscular male cats may have "high normal" levels of creatinine.

These kidney problems may be temporary or long-term depending on the underlying cause. In contrast to BUN levels which can be affected by stress, diet, and dehydration, creatinine levels are a better indicator of kidney function.

There are several conditions which may affect creatinine levels. High blood pressure, kidney stones, kidney infections and trauma may cause a sudden rise in creatinine and BUN levels. Once the high blood pressure or kidney problems are treated successfully, the BUN and creatinine will usually return to normal.

Dehydration, bleeding in the gastrointestinal tract (GI tract), or consumption of a high protein diet can increase creatinine levels. However, the BUN levels are likely to be more elevated than the creatinine levels. Once the problem has been resolved, the creatinine and BUN levels will typically return to normal.

Just as an aside regarding high protein diets, some cats are fed creatine supplements to build muscle stamina. Creatine is derived from amino acids and is normally produced in the liver, kidneys, and pancreas from the amino acids glycine, arginine, methionine. Creatine is also found normally in red meats and fish.

It is important to note that creatine does not build muscle; instead, it aids in the production of ATP which produces energy in the body. Further, there have been no long-term studies to determine the effects of prolonged use of creatine in cats. Ingestion of high levels of creatine can increase creatinine levels.

Pancreatitis or inflammation of the pancreas can elevate creatinine levels. Cats suffering from pancreatitis will appear "sicker" than cats with mild kidney problems. Once the pancreatitis has been treated, the creatinine levels should return to normal.

Diabetic cats with ketoacidosis or high ketone levels may also have elevated creatinine and BUN levels. In contrast to other conditions, the potassium and phosphorous levels will

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