Blood Test for Feline Kidney Disease

Under normal circumstances, the kidneys remove bodily waste from the blood and excrete it into the urine. When kidneys begin to fail or become diseased, these products build up in the blood. For this reason, blood tests are often a better indicator as to how the kidneys are doing then a urine test. Blood tests are essential in diagnosing and evaluating kidney disease in cats.

  1. Types of Blood Tests

    • There are two major types of blood tests typically given during an exam: a complete blood count and a blood chemistry test. A blood chemistry test will test the level of electrolytes, BUN, creatinine, cholesterol, glucose, liver enzymes and similar things while a complete blood count examines red and white blood cells.

    BUN Levels

    • A BUN blood test measures the blood urea nitrogen, a chemical that the liver makes from ammonia. BUN is then transferred and excreted by the kidneys. An increase in BUN in the blood indicates that the kidneys are not working correctly and is an indication of disease, dehydration and/or urethral obstruction. The normal range of BUN in cats is 14 to 36 milligrams per deciliter.

    Creatinine Levels

    • Creatinine is a breakdown product of muscle that is excreted by the kidneys at a constant rate. The normal range of creatinine in cats is 0.6 to 2.4 milligrams per deciliter. A high creatinine level in the blood indicates that the kidneys are not working correctly. According to the Feline CRF Information Center, elevated levels of creatinine and BUN indicates that approximately 70 percent of kidney function is gone.

    Calcium and Phosphorus Levels

    • A high level of phosphorous is another indication that the kidneys are not working. An increase in phosphorus will also cause calcium levels to increase, since a healthy cat needs have a calcium to phosphorus ratio between 1:1 to 2:1. The average level of calcium in a cat's blood is 8.2 to 10.8 milligrams per deciliter. The average level of phosphorous in a cat's blood is 2.4 to 8.2 milligrams per deciliter.

    Potassium Levels

    • Potassium is one of the few things that decreases in the blood during kidney disease. Potassium loss is caused by frequent vomiting and urination, two symptoms of kidney disease. The average potassium level in a cat's blood is 3.4 to 5.6 milliequivalents per liter.

    Charting Blood Tests

    • According to the Feline CRF Information Center, it is important to understand that blood tests can vary depending upon a number of factors. Things such as when your cat last ate or drank, its stress level, what vein was used and drugs given to the cat can all affect the results of a blood test. Be sure to request a copy of all lab work and use it to create a spreadsheet. This will allow you to see your cat's overall history and give a broader picture of its health.