An overactive thyroid is a condition vets discuss most often in middle-aged and older cats, and its signs can be easy to mistake for a cat simply getting livelier or fussier with age. In general terms the body speeds up, so a cat burns through food faster, drinks and urinates more, and gradually loses condition even while eating well. No single sign confirms it, which is why the whole pattern and a veterinary examination matter.
The appetite and weight mismatch
The most telling combination is a cat who eats eagerly, perhaps begging for extra meals, yet still loses weight over weeks. You may feel the ribs and hip bones more easily than before, or notice the face looking leaner in photographs. Because the appetite is good, owners often assume nothing serious is wrong, but steady weight loss alongside a strong appetite is exactly the mismatch worth reporting. Weighing an older cat at home every few weeks, using the same scales and time of day, gives you a real trend rather than an impression. A cat who is losing weight while eating less points in a different direction, so recording appetite beside weight keeps the two facts linked.
Restlessness, thirst and coat changes
Many cats with a faster-running system seem restless or more vocal, wander at night, or struggle to settle in their usual sleeping spots. Thirst often increases, so the water bowl empties faster and the litter tray holds larger wet patches than it used to. The coat can lose its smoothness, looking dull, matted or unkempt even in a cat who once groomed meticulously, and grooming itself may drop off. Some cats vomit intermittently or pass looser stools, and some feel warm or pant after minor exertion on a hot day. Each of these signs has other possible causes, from kidney trouble to diabetes, so treating them as a shared pattern to discuss, rather than a label to settle on at home, is the safer approach.
What a vet will want to check
A vet assessing these signs will usually feel the neck area, listen to the heart, check weight and condition, and talk about blood testing to measure thyroid hormone alongside kidney values and blood pressure. That combination matters because thyroid and kidney signs overlap heavily in older cats, and one can mask the other. Bring a clear record of when weight loss began, how appetite and thirst have changed, and any vomiting or night restlessness you have noticed. Details about current food, treats and any other health changes, such as new lumps or dental trouble, help the vet place this pattern in the wider picture of an ageing cat.
When to book rather than keep watching
Make an appointment soon if an older cat is visibly losing weight, drinking noticeably more, or seems persistently restless and unsettled. Seek a vet the same day if that cat stops eating, vomits repeatedly, breathes fast at rest or seems weak and wobbly. Gradual change is still change worth acting on in a senior cat, and earlier assessment gives more options than waiting until weight loss is advanced. Keeping the weight log, appetite notes and previous blood results together in your KinsLe Pet Passport, the portable packet for a cat's records, means every visit builds on the last set of numbers instead of starting again.