Deciding when a chronically ill or very elderly cat's quality of life has declined enough to consider euthanasia is one of the hardest decisions a cat owner faces, and there's no formula that removes the difficulty. There is, however, a more structured way to think through it than relying on instinct alone in the moment, and many veterinary hospice/palliative care specialists use some version of a formal quality-of-life assessment for exactly this reason.
The HHHHHMM Scale (and Similar Frameworks)
One commonly referenced framework (sometimes called the HHHHHMM scale, developed originally in veterinary hospice care) assesses several categories on a simple numeric scale: Hurt (is pain adequately controlled), Hunger (is the cat eating enough, with or without assistance), Hydration (similarly, for water intake), Hygiene (can the cat be kept reasonably clean, particularly if mobility is limited), Happiness (does the cat still show interest in normal things — family, environment, favored resting spots), Mobility (can the cat move around adequately to meet its own basic needs), and More good days than bad (tracking, even informally, whether bad days are becoming more frequent than good ones over time).
Why a Framework Helps
In the moment, especially with a beloved, longtime companion, it's genuinely hard to see decline clearly — gradual changes are easy to normalize day by day even as they add up to a real overall decline. Scoring categories somewhat separately, and especially tracking them over time (even informally, in a notebook or phone note) rather than relying purely on a single day's snapshot, can reveal a clearer trend than instinct alone in an emotionally difficult moment.
This Isn't About Reaching a Specific Number
No framework produces a definitive "this score means euthanize, this score means don't" answer — the value is in the structured reflection itself, and in giving you and your vet a shared vocabulary for a conversation that's otherwise very hard to have in the abstract. Your vet's professional assessment, combined with your own intimate knowledge of your cat's normal behavior and personality, together inform this decision more than any single scale can on its own.
The "More Bad Days Than Good" Signal
Many hospice-experienced vets point to this specific pattern — bad days beginning to outnumber good ones, tracked over real time rather than assessed in a single moment — as one of the more genuinely useful practical signals, precisely because it's less vulnerable to the day-to-day normalization problem described above.
You Are Not Wrong Either Way
There is no universally "right" time, and reasonable, caring owners arrive at this decision at different points for very similar situations. Whatever timing you reach, informed by your vet's guidance and your own honest assessment using a framework like this, is a legitimate, loving decision — not a failure or a rush, in either direction.
This is a sensitive topic. If you're currently facing this decision, your veterinarian is the best resource for guidance specific to your cat's situation, and many veterinary hospitals also have staff experienced in supporting owners through this process.