I need to say this before anything else: I am a web designer who lives with four cats. I am not a veterinarian, I have never played one on the internet, and nothing on this page is medical advice. What I can tell you is what fifteen-plus years of paying close attention to cats has taught me about when something is off, and what I do about it, which is always the same thing. I call the vet.
Cats are exceptionally good at hiding illness. In the wild, an animal that looks weak becomes something else's problem, so they evolved to act fine right up until they cannot. It is an impressive survival trait and it is deeply inconvenient for the people who love them. By the time a cat is obviously, visibly sick, the situation has usually been developing for a while.
I learned some of this the hard way with Minnie Mouse. She is the tuxedo who runs this house, the most photographed cat I own, and the most dramatic creature I have ever shared a roof with. Which meant that when she got quiet, I told myself she was just being moody. She was not being moody. I waited about four days longer than I should have. She was fine in the end, and I still think about those four days.
The only rule that matters: know your cat's normal
Every sign below is a change from baseline, not an absolute. Stripes sleeps fourteen hours a day and always has. That is normal for Stripes. If Luna slept fourteen hours a day I would be in the car. Luna does 3am zoomies into walls and I have simply accepted this as her operating system. A quiet Luna is a red flag. A quiet Stripes is a Tuesday.
So the useful skill is not memorizing symptoms. It is knowing, honestly, what each of your cats does on a boring day. Then anything that departs from that gets your attention.
1. Not eating for 24 hours or more
This is the one I treat as non-negotiable. A cat skipping a meal because you changed brands is one thing. A cat who has not eaten anything in a full day is a phone call, not a wait-and-see.
Cats do not handle going without food the way dogs or people do. Overweight cats are at particular risk when they stop eating. I am not going to explain the biology because I am not qualified to, but every vet I have ever talked to has been emphatic about this one, so I am passing that emphasis along. Twenty-four hours with no food, call your vet.
2. Hiding more than usual
A cat that suddenly wants to be under the bed, in the back of a closet, behind the water heater, somewhere they do not normally go, is often telling you they hurt or they feel wrong. Hiding is one of the most reliable signals there is and one of the easiest to talk yourself out of.
This is the exact one I fumbled with Minnie Mouse. She is dramatic by nature, so I filed it under personality. If a social cat goes antisocial for more than a day, that is not a mood, that is information. Call your vet.
3. Any change in litter box habits
I take this category more seriously than almost anything else on the list. Watch for:
- Going more often, or going much less
- Straining, or sitting in the box for a long time with little to show for it
- Crying or vocalizing while in the box
- Going outside the box when they never used to
- Blood, or urine that looks unusual to you
- Diarrhea lasting more than a day, or constipation
A male cat straining to urinate and producing nothing is treated as an emergency by every vet I have spoken to. Do not sleep on it, do not wait for morning, call.
The hard part in a multi-cat house is that you often cannot tell whose problem it is. Four cats, one box, one pile of evidence. This is genuinely the one place where the gadgets earn their keep. My Litter-Robot logs visits per cat, and having per-cat data instead of a household average is the difference between noticing a pattern in two days and noticing it in three weeks. It is not a diagnosis and it does not replace a vet. It just tells you sooner that you need one.
4. Drinking noticeably more water
If a cat who ignored the water bowl for years is suddenly camped at it, or hovering at the faucet, or draining the fountain twice as fast, pay attention. Increased thirst is commonly associated with kidney issues and diabetes, both of which are things vets want to catch early rather than late.
It often comes with more urination, so signs three and four tend to show up together. Either one on its own is worth a call.
5. Weight loss you did not plan
This one is sneaky because it happens slowly and you see your cat every day. Fur hides a lot. The trick is to use your hands, not your eyes. Run your hands along their spine and ribs once a week or so. If they are getting bonier and you did not change anything about their food, that is a call.
Weight loss while eating normally, or eating more than usual, is a combination that gets a lot of vets' attention. Do not sit on it.
6. Grooming that changes in either direction
A cat who stops grooming and starts looking greasy, matted or generally unkempt is often a cat who does not feel well or cannot comfortably reach. Common in older cats with joint pain, and easy to write off as "getting old."
The opposite counts too. Overgrooming to the point of bald patches or raw skin, especially in one specific spot, can point to pain, allergies, parasites or stress. Penelope had a stretch of licking one flank raw and I spent a week convinced it was behavioral. It was not. Call your vet.
7. Vomiting that goes past the occasional hairball
The internet has convinced a lot of people that cats just puke and that is normal. Some occasional hairballs, sure. Repeated vomiting, vomiting several days in a row, vomiting with any blood in it, or vomiting paired with not eating is not in the "cats be cats" category. That is a call.
8. Breathing that looks like work
Cats should breathe quietly and without visible effort. Open-mouth breathing, panting when they have not just sprinted around the house, rapid shallow breaths, wheezing, or a cat sitting with its neck stretched out and elbows away from the body are all things I would not wait on. That is an emergency vet call, not a next-week appointment.
9. Personality changes, including the grumpy kind
A gentle cat who suddenly swats when you pet a certain spot is usually not "turning mean." Pain makes animals defensive. Same goes for a cat who stops jumping onto furniture they have always used, hesitates at the stairs, or starts sleeping on the floor instead of their usual high perch.
Sudden clinginess counts as well. Any behavioral shift that lasts more than a couple of days deserves a conversation with your vet.
10. Bad breath, drooling, or dropping food
Cat breath is never great. Breath that makes you flinch from two feet away is different. Add drooling, pawing at the mouth, chewing on one side, or dropping kibble mid-bite, and you are usually looking at dental trouble, which is extremely common and extremely painful and something cats will absolutely hide from you. Your vet handles this one.
Go now, not tomorrow
Straining to urinate with nothing coming out. Labored or open-mouth breathing. Collapse or inability to stand. A suspected poisoning or toxic plant. Any trauma, including a fall or being stepped on. Repeated vomiting with no food or water staying down. Gums that look white, blue or grey.
Those are emergency clinic situations. Find your nearest 24-hour vet and put the number in your phone today, while nothing is wrong. I did that years ago and I have been grateful for it twice.
What actually helps you catch things early
- Annual vet visits at minimum. Every six months once a cat hits senior age. Bloodwork catches things your eyes never will.
- Hands on your cat weekly. Ribs, spine, belly, jaw. Thirty seconds of petting with intent.
- Actually look in the litter box. Every day. It is the single best health report you get.
- Feed something you trust and keep it consistent. I have fed my four Life's Abundance for years. Consistency also means changes in appetite are easier to spot.
- Write it down. A note in your phone with a date beats "I think it started maybe last week?" when your vet asks.
Here is the thing I most want you to take from this. Nobody at a vet's office has ever made me feel stupid for calling about something that turned out to be nothing. Not once in fifteen years. Waiting is the expensive mistake, both in money and in the part that actually matters. If your gut says something is off with your cat, your gut is working from more data about that specific animal than any article on the internet.
Make the call.
I am a cat owner, not a veterinarian. This article is general information from personal experience and is not a substitute for professional veterinary care. Some links on this page earn me a small commission at no additional cost to you.