Cats are generally considered "senior" starting around age 10-11, though this is a gradual transition, not a sharp line. Several things genuinely change during this period, and knowing what to watch for helps catch problems while they're still easy to manage.
What Becomes More Common
Chronic kidney disease, hyperthyroidism, diabetes, and osteoarthritis all become meaningfully more common in senior cats. None of these are inevitable, but all of them are common enough that many vets recommend more frequent checkups (every 6 months rather than annually) and routine senior bloodwork starting around this age, specifically to catch these conditions early — often before obvious symptoms appear, which matters because early treatment generally has better outcomes for all four of these conditions.
Weight Changes in Either Direction Matter
Unlike younger cats, where weight gain is the more common concern, senior cats can show meaningful weight loss as an early sign of several serious conditions (hyperthyroidism, kidney disease, dental disease making eating painful, or less commonly, cancer). A senior cat that seems to be eating normally but losing weight is a genuine reason for a vet visit, not something to attribute to "just getting older" without investigation.
Mobility Changes Are Often Under-Recognized
Osteoarthritis is now understood to be extremely common in senior cats — more common than owners typically realize, partly because cats hide joint pain well and partly because the signs (reduced jumping, stiffness after resting, reluctance to use stairs) are easy to attribute to general aging rather than a specific, often manageable condition. If your older cat seems to be jumping less or moving more stiffly, this is genuinely worth mentioning to your vet rather than assuming nothing can be done.
Practical Home Adaptations
Low-sided litter boxes (easier to step into with stiff joints), ramps or steps to favorite elevated spots, easily accessible food and water bowls (not requiring a jump or long walk), and keeping nails trimmed (senior cats often groom themselves less thoroughly) all make a real difference in comfort and quality of life.
What to Watch For
Increased thirst and urination (a classic early sign of several senior conditions including kidney disease and diabetes), any weight change, reduced grooming or coat quality, changes in litter box habits, and reduced activity or mobility are all worth mentioning at your cat's next checkup — or sooner if they're pronounced or sudden.
Regular veterinary care becomes more valuable, not less, as your cat ages — many senior conditions are very manageable when caught early, and "senior" doesn't have to mean declining quality of life.