Why guessing the bowl is the wrong move
When a cat starts a new medication, owners often adjust food by instinct — a little extra because she seems hungrier, a smaller bowl because she seems off her food. Both instincts can mislead. Some medicines increase appetite as a side effect without increasing the body's needs at all, so feeding to the new hunger quietly adds weight. Others cause mild nausea for the first days, and cutting the ration in response hides how much appetite has actually fallen. The amount question belongs in the prescribing conversation, answered for this specific medicine and this specific cat.
The questions to ask before the first dose
Ask whether the medicine should be given with food, on an empty stomach, or whether timing does not matter — this single answer shapes your whole feeding schedule, because a with-food medicine anchors naturally to a meal while an empty-stomach one may need a meal moved. Ask whether appetite change, in either direction, is an expected effect, and over what timescale: a cat who may be ravenous for a fortnight needs a different feeding plan from one who may pick at food for two days. Ask directly whether the daily food amount should change now, stay the same, or be reviewed at the follow-up — and whether weight should be checked at that visit, since gradual gain or loss is easy to miss by eye under a winter coat.
Also ask what counts as a reason to call: how many missed meals, how much extra hunger, or what kind of vomiting or loose stool should trigger a call rather than watchful waiting.
Watching appetite like it is data
For the first two weeks on a new medicine, keep a brief daily note: amount offered, amount eaten, whether the dose was taken easily, and any change in thirst, energy, or litter habits. Patterns in that log are far more useful to your vet than a general sense that she is 'eating a bit less.' If appetite surges, hold the ration your vet set and use play and puzzle feeding to answer the pestering, rather than enlarging meals — begging driven by a medicine feels exactly like genuine hunger to the cat, which is precisely why the vet's amount, not the cat's lobbying, has to govern the bowl.
If appetite falls, offer the normal food in smaller, more frequent portions at its usual warmth and place, and report a refusal that lasts beyond the window your vet named. Do not stop or alter the medicine itself because eating changed without discussing it first.
At the follow-up visit
Bring the log. Together with a weight check, it lets the vet judge whether any amount change is needed, whether the medicine is suiting your cat, and whether the food plan should shift for the months ahead. Long-term medicines deserve this review repeatedly, not once — appetite and weight drift slowly, and the cat who gained steadily across a season of increased hunger is far easier to help early.
Holding the prescription note, the food-timing rule, and your appetite log together in KinsLe in the Pet Passport keeps the complete medication-and-feeding packet ready for any vet visit or handoff.