
Start at HOME page When? Part 2
When your pet can no longer participate in many of the activities they once enjoyed, appears to be experiencing more pain than pleasure, is constantly confused or anxious, and definitely, when they stop eating, you should consider euthanasia (or, professional palliative care).
Especially difficult for some is when their own situations change & they are no longer able
to keep or care for their pet, or when home care becomes so burdensome there is a risk of becoming overwhelmed and even resentful. Even if not overtly sick, when that pet is elderly, extremely shy, has major ongoing medical needs or its behavior (which in some may be ‘normal’ - (urine marking in both dogs and cats)) makes it impossible for YOU to keep, before “rehoming” or relinquishing to a humane society, honestly consider if that makes it easier for you, but harder for them, & postpones the inevitable for an unadoptable animal. Especially if the pet is aggressive to humans or other animals, even if you make it known to a humane group or another person, you are morally & sometimes legally, responsible if that pet causes damage or hurts a person or another pet,
If you are convinced 're-homing' is not the responsible or right thing to do, it may take some time to find a veterinarian to euthanize a pet some would define as 'healthy'. I don't refuse in a hospital situation with technician help but generally decline "in-home" for aggressive, fractious or ferals, for safety reasons.
Regardless of the situation: terminally ill, critically injured, medical problems that require care more intensive & expensive than most can handle, subtle but inexorable decline; asking the question: "Does my pet have, or is it going to have, more bad days than good days?" can help you make the decision.
Lastly, although a pet can take a sudden turn for the worse, you shouldn't plan to wait until you "have to" -- because that likely will result in a trip to an emergency clinic, or the pet dying at home. No loving pet owner has ever said “Looking back, I did it too soon". You don't want to look back, worrying, or knowing, you waited to long.