Weight loss in cats is a sensitive indicator of many feline diseases. Because cats don't give us many clues when they are ill we take unexpected weight loss very seriously.
If a cat loses weight over a day or so then dehydration from a more rapid onset illness, pancreatitis or a gastrointestinal upset is more likely. We should correct the dehydration as soon as possible so don't hesitate to call us for advice or an appointment.
Even if your cat seems otherwise well and happy, weight loss over a month or more could be due to diseases such as hyperthyroidism, kidney disease, diabetes, inflammatory bowel disease or cancer. It is only when these diseases are well advanced that a cat will finally show obvious signs.
When your cats come in for a regular exam the first thing we do is weigh them. We take weight loss very seriously and if you haven't been intentionally dieting them we will recommend tests. Hyperthyroidism, diabetes and kidney disease are detected with tests we do in our own laboratory. Results are available within half an hour. If we don't find anything then we discuss the possibility of bowel disease or other more unusual diseases.
It is always better to detect and manage disease earlier rather than later. Cats often have chronic ongoing disease. With good management we can improve their quality of life and ensure they live a good long life with you.