Cat not eating
Cats are not small dogs when they skip a meal. A dog can miss breakfast and be fine. A cat who does not eat, especially an overweight cat, can develop hepatic lipidosis, a liver crisis that starts after only a few days without calories. Treat a quiet food bowl as a medical clue.
How fast to call
If your cat has eaten nothing for about 24 hours, call a clinic the same day. Call sooner if the cat is hiding, losing weight, vomiting, drooling, or breathing with the mouth open. Kittens who skip two meals should not wait overnight. A cat who is interested in food and then walks away, or who chews on one side, may have a painful mouth rather than a picky mood.
Drooling, a pawing at the face, or a foul smell from the mouth points toward dental disease, a foreign body under the tongue, or mouth ulcers. Kidney disease, pancreatitis, and intestinal disease often show up as nausea: the cat sits by the bowl, licks its lips, and leaves. You will not sort those apart from the kitchen.
What you can check at home
Confirm the cat is not locked in a closet or eating in a different room. Make sure another pet is not guarding the bowl. Offer the usual diet, slightly warmed, in a quiet place. Do not start a cupboard tour of fish, milk, and deli meat. A cat who feels sick may eat the novelty once and then refuse everything, including the food you will need later for medications.
Count the litter box. No urine, or straining, changes the problem into a possible urinary obstruction, which is an emergency in male cats and is covered on the cat urinary page. No stool plus a tight belly also deserves a same-day exam.
At the clinic
Expect questions about weight trend, thirst, vomiting, and whether the appetite crash was sudden. Bloodwork is common because kidney disease and liver stress do not have a reliable home test. If the cat has already gone several days without food, the veterinarian may talk about appetite stimulants, anti-nausea medication, or a feeding tube. A tube sounds drastic and is often the kindest way to get calories in while the cause is treated.
Do not give human pain medicine, essential oils on the chin, or "just a little" of a dog's medication. Use the when-to-see-a-vet checker and the vet help hub for the next step.
Sources
Clinic decisions belong to the veterinarian who can examine the animal. This page is background reading.
Cat appetite questions
How long can a cat go without eating?
Call a veterinarian if a cat skips more than a day of calories. Overweight cats can develop hepatic lipidosis after only a few days of not eating.
Is it hairballs?
A single hairball in a cat who then eats is common. Repeated retching or a cat who will not touch food is a medical visit.
Should I offer tuna to tempt a cat?
A taste of a familiar food is fine. A long stretch of tuna, milk, or a new raw diet is not a treatment for nausea or dental pain.