How to tell if your cat is sick

Your cat just spent the entire morning hiding under the bed, hasn’t touched their favourite tuna treats, and when they finally emerged, something just felt… off. Sound familiar?

Here’s the thing about cats — they’re absolute masters at hiding illness. It’s hardwired into their DNA from their wild ancestors, where showing weakness meant becoming someone’s dinner. So by the time your indoor fluff ball is obviously unwell, they might have been feeling rough for days or even weeks.

I learned this the hard way with my tabby, Oscar, about eight years ago. He seemed fine one day, maybe a little quieter than usual, and by the next evening he was lethargic and refusing food entirely. The vet visit revealed a urinary blockage that could have been fatal if I’d waited another day. That experience taught me to trust my gut when something feels different about my cats, even if I can’t put my finger on exactly what.

The Subtle Signs That Scream “Something’s Wrong”

Cats won’t limp dramatically or whimper when they’re hurting. Instead, they’ll do things like sleep in a different spot than usual or eat standing up instead of lying down. These tiny changes are often the first red flags.

Changes in eating habits are massive indicators. And I don’t just mean completely stopping eating — though that’s obviously a veterinary emergency. I’m talking about eating more slowly, chewing on one side of their mouth, or suddenly becoming picky about food they’ve loved for years. When my senior cat Maisie started leaving half her wet food untouched after years of licking the bowl clean, it turned out she had dental pain that was making eating uncomfortable.

Litter box changes tell you everything. Cats are creatures of habit, so when they start peeing outside the box, straining to urinate, or producing unusually small amounts of waste, pay attention. I cannot stress this enough — any change in urination patterns, especially in male cats, needs immediate veterinary attention. Urinary blockages can kill within 24-48 hours.

But here’s what really gets me — people often dismiss behaviour changes as “just getting older” or “being moody.” Your social butterfly suddenly hiding all day isn’t having an attitude problem. Your lap cat who won’t let you touch them anymore isn’t being dramatic. These personality shifts are often pain or illness talking.

The Physical Signs You Can Actually See

Some symptoms are harder to miss, thankfully. Vomiting occasionally? Probably not a crisis if they’re otherwise normal. But vomiting multiple times in a day, especially if nothing’s coming up or there’s blood involved, means it’s time to make that phone call to your vet.

Breathing changes are serious business. Cats normally breathe quietly and effortlessly. If you can see their sides heaving, they’re breathing with their mouth open (outside of being stressed at the vet), or they’re making noise when breathing, that’s an emergency situation.

Weight loss creeps up on you because you see your cat every day. I started weighing my cats monthly after missing Maisie’s gradual weight loss over several months. A kitchen scale works perfectly — just weigh yourself, then weigh yourself holding the cat and do the math. Sudden weight gain can be just as concerning, especially if their belly looks distended.

And look — I know this sounds gross, but you need to pay attention to what’s happening in the litter box. Changes in urine colour, blood in stool, diarrhoea lasting more than a day, or straining without producing anything are all red flags waving frantically at you.

When “Waiting to See” Becomes Dangerous

Every cat owner has been there — it’s 2 AM, your cat seems off, and you’re wondering if you’re overreacting. Here’s what I’ve learned after fifteen years and way too many late-night vet visits: trust your instincts, but also know which symptoms can’t wait.

Difficulty breathing, inability to urinate, repeated vomiting, signs of severe pain (like yowling when touched), or complete lethargy require immediate attention. Not “first thing Monday morning” attention — right now attention.

But what about those grey areas? Your cat seems a little sluggish, maybe ate less breakfast than usual, but isn’t showing obvious distress. Fair warning — this is where it gets tricky. I’ve found it helpful to give myself a timeframe. If they’re not back to normal within 12-24 hours, or if any additional symptoms appear, we’re heading to the vet.

Temperature can be telling if you’re brave enough to take it. A cat’s normal temperature is between 100.5-102.5°F. Anything outside that range, especially if combined with other symptoms, warrants a call to your vet. Honestly though, most cats are less than cooperative about rectal thermometers, so don’t feel bad if you skip this step.

The Age Factor Changes Everything

Senior cats — generally considered 7+ years old — need extra vigilance. They’re masters at compensating for age-related issues until they simply can’t anymore. Weirdly enough, some of the most serious conditions in older cats start with incredibly subtle symptoms.

Kidney disease, hyperthyroidism, and diabetes are all common in senior cats, and they all start with vague signs like increased drinking, slight weight loss, or minor changes in behaviour. Your 12-year-old cat isn’t necessarily “just slowing down” — they might be dealing with something treatable if caught early.

Young cats present their own challenges because everything is new to you as an owner. Is this normal kitten energy followed by a crash, or are they actually unwell? Generally, healthy kittens are either 100% on or completely crashed out sleeping. A listless, moderately active kitten is often a sick kitten.

Products Worth Trying

Pet Scale — Monthly weigh-ins have caught health issues early in my crew more than once, and a dedicated pet scale takes the guesswork out of tracking weight changes.

Water Fountain with Measurement Markings — Changes in water consumption are huge health indicators, and this fountain makes it easy to monitor how much they’re actually drinking.

Wireless Pet Camera — Being able to check on your cat’s behaviour throughout the day when you’re not home has given me peace of mind and valuable information to share with my vet.

Digital Pet Thermometer — For those brave enough to take temperatures, this one is designed specifically for pets and gives quick, accurate readings.

Trust Your Gut, But Know Your Cat

The good news is that you know your cat better than anyone. You know how they normally move, eat, sleep, and interact. When something feels different, it probably is different. I’ve never regretted a precautionary vet visit, but I have regretted waiting too long.

Keep a simple log if you’re concerned — eating, drinking, litter box use, and general behaviour. Even a day or two of notes can help your vet tremendously and might reveal patterns you hadn’t noticed.

And here’s something vets won’t always tell you upfront — if you’re genuinely worried but can’t pinpoint why, that’s valid information. I’ve brought cats in on nothing more than “something feels wrong,” and more often than not, the vet found something subtle I’d missed.

Your cat is counting on you to be their voice and their advocate. They can’t tell you their stomach hurts or that it’s getting harder to jump onto their favourite perch. But they’re constantly communicating through their behaviour, eating habits, and daily routines.

Have you noticed subtle changes in your cat that turned out to be early signs of illness? I’d love to hear about your experiences in the comments — sometimes sharing these stories helps other cat parents recognize similar patterns in their own furry family members.