Weight loss in an older cat is easy to miss at first, especially under a full winter coat, and it's one of the most common reasons senior cat owners end up at the vet. Here's what's usually behind it, and how to tell what's worth worrying about.
The most common cause: hyperthyroidism
An overactive thyroid is one of the top reasons senior cats lose weight, even while eating normally or more than usual. Other signs include increased thirst, restlessness, and a faster heart rate. It's diagnosed with a simple blood test and very treatable.
Kidney disease
Chronic kidney disease is common in cats over ten. Weight loss is often paired with increased thirst and urination, and sometimes a poor coat or bad breath. Early-stage kidney disease can be managed for years with diet and monitoring.
Dental pain
If chewing hurts, cats often eat less without owners noticing right away. Look for dropping food, favoring one side of the mouth, or reduced interest in dry kibble specifically.
Diabetes
Weight loss alongside a bigger appetite and more frequent urination can point to diabetes, which is manageable with insulin and diet changes once diagnosed.
Simply eating less
Sometimes it's less medical and more about routine: stress from a household change, a new pet, or even mild depression can reduce a cat's appetite gradually.
What to watch for at home
Weigh your cat monthly if possible, even a simple bathroom scale trick (weigh yourself holding the cat, then subtract your own weight) works. A loss of more than 10 percent of body weight over a few months is worth a vet visit regardless of the cause.
When to call the vet
Any noticeable weight loss in a senior cat deserves a checkup, even if they still seem happy and active. Cats are good at masking illness, and catching thyroid, kidney, or diabetes issues early makes a real difference in how manageable they are long term.