Senior cats are at an age when several things can go wrong at the same time. However, many diseases are treatable so don't simply put any changes in your cat down to 'old age' and ignore them!
Problems such as a hyperactive thyroid (hyperthyroidism), high blood pressure, kidney disease, diabetes and cancer are more likely to occur at this stage. Cats can also suffer from the equivalent of senile dementia, although signs can be confused with other diseases so it is important to establish a proper diagnosis. Older cats with failing kidneys may not drink sufficiently and can become dehydrated and constipated. They may spend less time grooming, leading to coat and skin problems or brittle overgrown claws, and may eat less because their sense of smell is not so acute or they have teeth or gum problems. Arthritis is also common in the senior group.