How do you care for an ageing pet?
By changing the environment and the monitoring, not just the veterinary care — because most of what makes an old animal comfortable is practical, and most of what makes them uncomfortable is treated as "just old age" when it is a treatable condition.
The central correction: "slowing down" is not a diagnosis. Reduced activity, reluctance to jump, stiffness after rest, irritability and altered sleep are frequently pain — most commonly osteoarthritis, which is very common in older dogs and cats and is substantially under-diagnosed in cats because they hide it. Cats do not limp; they stop jumping, and owners read it as age.
What changes physiologically: joints; kidney function, particularly in cats; heart function; dental disease, which is painful and extremely common; sight and hearing; cognitive function; weight, in either direction; and immune competence.
What should change practically:
More frequent veterinary checks, commonly twice yearly, with blood and urine screening — which detects kidney disease, hyperthyroidism and diabetes before symptoms, when management is far more effective.
Environmental adaptation, which does more for quality of life than most interventions: ramps and steps; non-slip flooring, since hard floors are genuinely difficult for arthritic animals; raised food and water bowls; litter trays with a low side, which is the single most useful change for an old cat; more trays, closer; warm, supported bedding away from draughts; and night lighting for failing sight.
Diet, adjusted for condition rather than for age alone.
Exercise maintained but modified — shorter and more frequent, since stopping accelerates decline.
Pain relief, which is the most under-used intervention and transforms behaviour in animals assumed to be simply old.
Cognitive dysfunction — disorientation, altered interaction, sleep reversal, house soiling, anxiety — which is recognised, is treatable to a degree, and is frequently mistaken for stubbornness.
Grooming assistance, since old animals groom themselves less and mats cause pain.
Monitoring quality of life deliberately, using a written scale rather than memory, which makes changes visible and supports end-of-life decisions.
General information, not veterinary advice.