The four stages
The 2021 AAHA and AAFP feline life stage guidelines split it like this, and unlike the dog guidelines these are plain age bands, because cats vary far less in size than dogs do.
| Stage | Age | What it means in practice |
|---|---|---|
| Kitten | Birth to 1 year | Vaccination course, neutering, and the social window |
| Young adult | 1 to 6 years | Yearly exam. Watch weight and teeth |
| Mature adult | 7 to 10 years | Start checking kidneys, thyroid, blood pressure |
| Senior | Over 10 years | Twice-yearly exams, yearly bloodwork and urine |
The human-years conversion
International Cat Care puts the first two years at about 24 human years together, then roughly four human years for each cat year after that. So a 3-year-old cat is around 28, and a 15-year-old cat is around 76.
Sources differ on how to split that first 24 — some put year one at 15 and year two at 9. They all agree on where a two-year-old lands and on the four-a-year afterwards, so the disagreement is not worth much.
The three things that change with an older cat
- Drinking more. The earliest visible sign of kidney disease and of diabetes, and the easiest to miss in a multi-cat house. If you are refilling the bowl more often, say so.
- Losing weight while still eating. In a cat over seven this is hyperthyroidism until proven otherwise, and it is very treatable.
- Stopping jumping. Studies using X-rays find arthritis in the large majority of older cats, and almost none of them are being treated for it, because cats do not limp — they just stop doing things.
None of those look like an emergency, which is exactly why they get left. A twice-yearly exam after ten is the AAHA recommendation and it exists because of this list.