Why Is My Old Cat Losing Weight? | Companion Animal Veterinary Hospital
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Why Is My Old Cat Losing Weight?

An old tabby cat with a white nose and chest looking up at the camera

Part 1

Most of us have seen an older cat, often with an unkempt coat, that has gone from a previously healthy individual to a thin, bony animal in the space of a few months. While there are any number of reasons a cat can lose weight, there a 3 specific conditions that we often see in older cats:

  • Chronic Kidney Disease
  • Diabetes
  • Hyperthyroidism

Chronic Kidney Disease

Chronic Kidney Disease (CKD) is the progressive and permanent loss of kidney function over time. Kidneys perform a number of essential functions and their loss results in a variety of health problems for your cat.   

Kidneys filter the blood of breakdown products and toxins. Damaged kidneys fail to do this adequately, resulting in signs of lethargy, nausea, reduced appetite and weight loss. Conversely, proteins may be lost in the urine, further contributing to weight and appetite loss.

Kidneys are also involved in blood production, so damage may result in pale gums and weakness caused by low red blood cell numbers. Increased drinking and urination is often seen in affected cats as their kidneys lose the ability to conserve water, while blood pressure is often raised causing damage to various organs.  

Diagnosing CKD is done by a combination of blood and urine tests. These tests may need to be repeated to confirm the diagnosis and monitor progress.

The cornerstone of treatment is dietary modification, specifically changing to one that is tailored to the specific needs of cat with CKD. It can be difficult to change the diet once cats are feeling unwell, so it is best to change as soon as possible and to closely manage a slow transition to the new food.  Medication may be used to deal with high blood pressure and urine protein loss.


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