If you visit the veterinarian regularly with your dog or cat, there is a good chance that you will hear the term “creatinine levels.” So what is creatinine, and why do we test for it?
Creatinine is a breakdown product of creatine phosphate, which is a normal component of muscle and is removed from the blood primarily by filtration through the kidneys. Veterinarians measure creatinine levels because it helps to identify kidney problems.
Creatinine levels have been used reliably to evaluate kidney disease for a long time. There are limitations to the use of this test in the early diagnosis of kidney disease and in dogs and cats with loss of muscle mass. A new test, symmetric dimethylarginine (SDMA), has recently been developed for dogs and cats to support earlier and more reliable diagnosis of kidney disease. Your veterinarian will generally run these tests simultaneously to get an accurate assessment of how well your pet’s kidneys are working.
What can creatinine say about the kidneys?
The primary job of the kidneys is to remove waste chemicals from the body and excrete them as urine. Veterinarians measure chemicals that should be appropriately removed by your kidneys to determine if the kidneys are doing their job properly. Therefore, kidney disease is generally detected and evaluated by measuring the levels of certain chemicals, like creatinine, in the blood or urine.
What could low creatinine levels mean?
Low levels of creatinine can indicate poor muscle health or severe liver disease. Creatinine can also be lowered by increased metabolic states caused by hyperthyroid disease or extreme weight loss associated with muscle depletion. Lower than normal creatinine levels may occur when pets are fed extremely protein deficient diets resulting in poor muscle mass.
What could high creatinine levels mean?
Elevated levels of creatinine occur when the filtration rate of the kidneys is inadequate to remove this waste product. The importance of increased creatinine is that it indicates decreased kidney filtration but is not specific for kidney disease. This is why it is important to have your dog or cat tested for SDMA levels along with creatinine. Creatinine levels increase only when there is significant loss of kidney function and your dog or cat already likely has advanced renal disease. SDMA will aid in earlier identification of kidney disease when interpreted by your veterinarian in conjunction with creatinine levels.
How is creatinine measured and interpreted?
Creatinine is measured by chemical analysis at a laboratory. Since normal levels of creatinine are typically quite low and increases occur incrementally with time, one individual blood level might not mean much to your veterinarian. Interpretation of creatinine levels requires a complete assessment of the ability of the kidneys to eliminate creatinine.
The amount of blood the kidneys can filter in 24 hours is called creatinine clearance, but collecting urine for 24 hours is inconvenient. The alternative involves a calculation of the filtration rate, which is more convenient but has the potential to be misinterpreted.
Creatinine is a valuable test but is insufficient on its own to diagnose kidney disease because when levels are elevated in the blood, your cat or dog has already lost the majority of kidney function.
Learn more about kidney disease testing >
If you have any questions or concerns, you should always visit or call your veterinarian – they are your best resource to ensure the health and well-being of your pets.