Start with the clinic's instructions, not guesswork
Preparation begins with the specific instructions your own clinic gives you, because the right fasting window and arrival time depend on the procedure your cat is booked for and on your cat's age and health. Read the appointment message carefully as soon as it arrives, and call the practice if any part of it is unclear rather than improvising on the morning. Tell the team in advance about anything that has changed since the booking was made: a reduced appetite, a bout of sickness or loose stool, new lumps you have noticed, or anything you have given your cat at home, however minor it seems.
Keep your cat indoors from the evening before.
The night before and the morning of the procedure
Remove food at the time your clinic specifies and leave water arrangements exactly as they advise, since guidance on drinking varies with the procedure. It helps to feed the last permitted meal a little earlier in the evening and to lift any food bowls belonging to other pets too, so a determined cat cannot help herself to a housemate's supper.
Practise the carrier before it matters. If the carrier only appears on vet days, most cats vanish at the sight of it. Leaving it out open for several days with a familiar blanket inside lets your cat walk in and out voluntarily, and feeding a favourite meal inside it once or twice can soften the association further. On the morning, line it with bedding that smells of home, secure the door properly, and cover the carrier with a light blanket in the car to cut down visual stimulation on the journey.
What the team does while your cat is asleep
Once admitted, your cat is checked over before the procedure, and the team monitors breathing, heart function and temperature throughout while she is asleep. You do not need to manage any of that side of the day, but it helps to be reachable by phone for the whole period, to keep the volume up on your handset, and to know in advance roughly when the clinic expects to call with an update.
The first evening back home
Most cats come home groggy, wobbly on their feet and keen to sleep, and some are unusually clingy or unusually keen to hide. Set up one warm, quiet room in advance with bedding on the floor rather than up high, a litter tray within easy reach, and water nearby, and keep children and other pets out until your cat is steady again.
Offer food only in the way the clinic advised; a small, light meal is commonly suggested once a cat is fully awake and interested, but the discharge note for your cat's procedure outranks any general habit. Check any wound or shaved area without pressing on it, follow the guidance you were given about collars or coverings, and keep outdoor cats inside for as long as the team directed.
Changes that mean you should call the clinic promptly
Call the practice the same day if your cat has not come round properly over the expected recovery period, refuses all food well beyond the window the team described, vomits repeatedly, or seems to be in obvious discomfort that is not settling. Bleeding from a wound, swelling that is growing, a wound that opens, laboured breathing, or a cat who cannot be roused comfortably are reasons to phone immediately rather than wait until morning, using the out-of-hours number the clinic gave you if the practice is closed. A short written note of when you noticed each change, and a photo of a wound taken from a distance, gives the team something concrete to triage from. Having those past procedure dates, weight notes and discharge details stored together in KinsLe's Pet Passport makes that follow-up call calmer, because you can describe your cat's recent history accurately instead of reconstructing it from memory.