If you ask most cat owners how they knew something was wrong with their cat, they'll say something like: "She just seemed off." That instinct is real — but it can take days or even weeks to crystallize, because cats are remarkably good at appearing normal even when they're not.
This isn't stubbornness. It's ancient biology. Cats evolved as both predators and prey, and showing vulnerability in the wild meant becoming a target. So their default is to suppress any signal of illness until they can't anymore. By the time a cat is overtly sick, things are often more serious than they initially appear.
The good news is that the early signs are learnable. Here are ten of the most common — and most commonly missed — indicators that something may be wrong.
1. A change in appetite — especially gradual
Eating noticeably less over several days, picking at food and walking away, or showing less enthusiasm for meals that previously excited her.
A single skipped meal is rarely alarming. But a cat who eats noticeably less over three to five days is telling you something. Decreased appetite is one of the most universal early responses to illness — it shows up across everything from dental pain to kidney disease to cancer.
The tricky part: a gradual decrease is easy to normalize. If your cat goes from eating 95% of her food to 70%, it might not register as a problem until she's already down to 40%. Consistent logging is what makes the trend visible.
2. Hiding or increased solitude
Spending significantly more time alone in unusual places — under the bed, inside closets, behind furniture — especially if she normally seeks contact.
Hiding is one of the most consistent behavioral signs of pain and illness in cats. It's instinctive: when something is wrong, the safest strategy is to be invisible. A cat who suddenly starts spending hours in places she rarely used to visit is worth paying close attention to.
This is especially significant if the behavior is new. A cat who has always been independent and private is different from a social cat who abruptly withdraws.
3. Changes in water intake
Drinking noticeably more water than usual, spending more time at the water bowl, or seeking water from unusual places like faucets or standing water.
Increased thirst — the medical term is polydipsia — is a classic early sign of three of the most common feline illnesses in adult and senior cats: chronic kidney disease, hyperthyroidism, and diabetes mellitus. All three are manageable if caught early, and significantly harder to manage once advanced.
Many cat owners never notice increased drinking because cats are private about it. If you have multiple cats, it's even harder to track. This is one of the reasons daily health logging — per cat — matters so much.
4. Litter box changes
Urinating more or less frequently, straining without producing output, stool that is unusually loose or hard, blood in urine or stool, or avoiding the litter box entirely.
The litter box is one of the most informative health monitoring tools you have access to, and most owners check it less than they should. Changes in urinary output, stool consistency, or frequency all reflect what's happening internally.
Important: a male cat straining in the litter box with little or no urine output is a medical emergency. Urinary blockages in male cats can become fatal within 24 to 48 hours if untreated. Don't wait to see if it resolves.
5. Coat condition and grooming changes
A coat that looks dull, greasy, or matted; patches of thinning or bare fur from over-grooming; or a cat who has stopped grooming herself as she normally would.
A healthy cat's coat is smooth, clean, and consistent. When something is wrong — whether it's pain, nausea, or systemic illness — grooming is often one of the first things to go. A cat who is too uncomfortable to reach certain areas, or simply too depleted to maintain her routine, will develop a noticeably deteriorated coat within a week or two.
On the other end, excessive grooming to the point of bald patches can indicate stress, allergies, or a skin condition. Both extremes are worth noting.
6. Unexplained weight loss
Feeling ribs more prominently than before, visible spine or hip bones, clothes hanging differently — even without a change in eating behavior you've noticed.
Cats lose weight for many reasons — hyperthyroidism, cancer, dental disease, inflammatory bowel disease — and in many cases, the weight comes off slowly enough that owners don't notice until it's significant. A pound of weight loss on a ten-pound cat is equivalent to about fifteen pounds on an average adult human.
You don't need a scale to detect this. Run your hands along her sides and feel her ribs. They should be palpable with light pressure but not clearly visible. If you can feel them more easily than you used to, that's a meaningful change.
7. Lethargy or reduced activity
Sleeping more than usual, less interest in play or interaction, not jumping to usual spots, or a general sense of low energy that persists beyond a single lazy day.
Cats sleep a lot normally — up to 16 hours a day is typical. This makes lethargy hard to identify from a single observation. What you're looking for is a pattern change from her normal baseline: a cat who usually greets you at the door and doesn't, a cat who usually plays at a certain time and shows no interest, a cat who normally jumps to the windowsill and has been on the floor for days.
Context matters. One low-energy day after a stressful event like travel or a vet visit is expected. A week of reduced activity is not.
8. Changes in vocalization
Crying, yowling, or making sounds she doesn't usually make — especially at night; conversely, a usually vocal cat becoming unusually quiet.
Increased vocalization can indicate pain, cognitive dysfunction (common in senior cats), hyperthyroidism, or anxiety. A cat who suddenly starts yowling in the night — especially an older cat — deserves a vet evaluation.
Quieter than normal is also notable in a typically vocal cat. Both directions from baseline warrant attention.
9. Breathing changes
Any panting, open-mouth breathing, rapid shallow breaths, labored breathing, or a hunched posture with elbows turned out.
Cats should not pant. Ever. Unlike dogs, open-mouth breathing in a cat — unless it occurred during extreme exertion or in severe heat for a very brief moment — is abnormal and requires immediate veterinary attention. The same goes for visible effort to breathe, rhythmic abdominal movement while breathing, or a cat sitting with her elbows splayed out to open her chest.
Breathing problems in cats can escalate quickly. Don't take a wait-and-see approach.
10. Eye, ear, or nose discharge
Discharge around the eyes (cloudy, yellow, or crusty), dark or smelly debris in the ears, a runny nose, or visible third eyelid (a pale membrane in the inner corner of the eye).
Clear discharge from the eyes or nose in small amounts can be normal. Colored discharge — yellow or green — suggests infection. Persistent eye discharge, visible third eyelid (nictitating membrane), or squinting can indicate eye injury, upper respiratory infection, or systemic illness. Ear discharge or odor is almost always a sign of infection or ear mites.
What to do when you notice a change
Most changes warrant a day or two of closer monitoring rather than an immediate emergency visit — with some exceptions. Here's a quick guide:
Monitor for 2–3 days if: Slightly reduced appetite, mild lethargy, coat change, minor vocalization shift, small change in litter box habits.
Call your vet for a same-week appointment if: The change persists beyond 3 days, multiple signs appear together, or your gut says something is wrong even if you can't name it.
Go immediately if:
Straining in the litter box without producing urine — especially in male cats
Open-mouth breathing or visible breathing difficulty
Complete refusal to eat for more than 24 hours
Sudden inability to stand, walk straight, or respond normally
Visible blood in urine or stool
Collapsed or unresponsive
Why tracking matters more than memory
The challenge with all of these signs is that they're easy to normalize when you see your cat every day. A gradual change is almost invisible in real-time — it's only obvious in retrospect.
Keeping a daily log — even just a quick note on appetite, energy, and litter box — creates the reference point that makes change visible. When you can see that your cat's appetite has been decreasing for six days, or that she's been hiding more for the past week, you have something concrete to act on.
Apps like Cat360 are built for exactly this kind of lightweight daily logging. A 30-second check-in per day turns into a wellness trend that can catch problems early — and gives your vet actual data to work with when you bring it in.
You don't need to become a feline medical expert. You just need to know your cat's normal — and notice when it shifts.
Frequently asked questions
How can you tell if a cat is in pain?
Cats in pain often hide, become less active, stop grooming, or show subtle facial changes — squinting, flattened ears, or a hunched posture. They rarely vocalize pain the way dogs do. Tracking behavioral changes daily is the most reliable way to notice something is wrong.
What does a sick cat act like?
A sick cat typically shows one or more of: reduced appetite, increased hiding, less interest in play, changes in litter box use, unusual vocalization, weight loss, a dull or unkempt coat, or decreased grooming. The key is a change from their normal baseline.
When should I take my cat to the vet for being sick?
Book a vet visit if symptoms persist for more than 2–3 days, or immediately if you see: complete refusal to eat for 24+ hours, labored breathing, straining in the litter box with no output, inability to walk normally, or visible blood in urine or stool.
Do cats hide when they are sick?
Yes — hiding is one of the most consistent signs that a cat is unwell or in pain. It is an instinctive survival behavior. A cat that suddenly spends significantly more time alone in unusual places is worth monitoring closely.
