How to Know If Your Cat Is Sick: 7 Warning Signs to Watch For

Last updated on October 9th, 2025 at 04:03 pm

You know that moment when something feels… off? Maybe your cat didn’t greet you at the door like usual, or they walked past their favorite toy without a second glance. It’s subtle, but your gut is telling you something’s different.

Here’s the tricky part: cats are incredibly skilled at masking illness. By the time our house cats show obvious signs of being unwell, they may have been suffering quietly for days or even weeks. This evolutionary behavior is deeply ingrained—but more on that in a moment.

I learned this firsthand with my cat, Franklin. One day he seemed perfectly fine, and the next he was clearly not feeling well. Looking back, I wonder if there were subtle signs I had missed. Thankfully, we got him the treatment he needed, and he’s doing great now—but that experience taught me how important it is to know what to watch for.

That’s exactly why I wanted to put together this guide. Once you know what to look for, you can catch those subtle changes early—before it becomes serious. Keep reading to learn more about the warning signs that every cat parent should have on their radar.

Why Cats Hide Their Illness (And Why That Makes Our Job Harder)

Before we get into the warning signs, here’s something important: in the wild, showing weakness makes cats vulnerable to predators. Even though Mr. Whiskers hasn’t faced a predator in his entire pampered life, that instinct is still hardwired. This means your cat might be feeling pretty awful before they actually show it, so knowing what to look for is important!

How to Know If Your Cat Is Sick: 7 Signs

1. Changes in Eating Habits or Weight

Has your food-obsessed kitty suddenly turned up her nose at dinner? Or maybe your picky eater is suddenly ravenous all the time? Either extreme is worth paying attention to.

A decrease in appetite could point to dental pain (yes, cats get toothaches too!), digestive issues, or nausea. On the flip side, increased appetite paired with weight loss can be a red flag for hyperthyroidism, which is common in older cats.

What to watch for: Skipping meals for more than a day, difficulty chewing, dropping food while eating, or noticeable weight changes you can feel when petting your cat.

2. Unusual Lethargy or Restlessness

We all know cats sleep a lot. But there’s a difference between normal cat napping and “I literally can’t be bothered to move” lethargy. If your typically playful kitty has no interest in their favorite treats or seems unusually withdrawn, something might be up.

On the other hand, restlessness—like pacing, inability to get comfortable, or excessive meowing—can signal pain or anxiety.

Trust your gut: You know your cat’s normal energy level better than anyone!

3. Coat and Skin Issues

A healthy cat has a shiny, smooth coat and takes grooming very seriously. When cats don’t feel well, grooming is often the first thing to go. You might notice their fur looking greasy, matted, or dull.

Other skin red flags include:

• Excessive scratching or licking one area
• Bald patches or thinning fur
• Flaky skin or dandruff
• Any lumps, bumps, or swelling

These can indicate allergies, parasites (like fleas), nutritional deficiencies, or even stress.

4. Drinking More Water or a Change in Litter Box Habits

This is a big one when figuring out how to know if your cat is sick. If you’re suddenly refilling the water bowl way more often, or the litter box is soaked through daily, pay attention.

Increased thirst and urination can be early warning signs of:

• Diabetes
• Kidney disease
• Hyperthyroidism
• Urinary tract infections

Also watch for straining in the litter box, crying while urinating, or accidents outside the box—especially in male cats, as urinary blockages can become life-threatening fast.

5. Vomiting or Diarrhea

Sure, the occasional hairball is normal (though not fun when it’s on your carpet). But frequent vomiting, especially if there’s blood or it’s paired with lethargy, is concerning. Same goes for diarrhea that lasts more than a day or contains blood.

These digestive issues could indicate anything from eating something they shouldn’t have to inflammatory bowel disease or parasites.

6. Behavioral Changes

Cats are creatures of habit, so when their behavior shifts, it’s often telling us something. Your social butterfly suddenly hiding under the bed? Your lap cat now hissing when you try to pet her? These personality changes matter.

Other behavioral red flags:

• Increased aggression or irritability
• Hiding more than usual
• Excessive vocalization (especially at night)
• Confusion or disorientation

Pain, illness, and even cognitive decline in older cats can all cause behavioral shifts.

7. Breathing Changes or Coughing

Healthy cats breathe quietly and evenly. If you notice open-mouth breathing (when they’re not stressed or hot), rapid breathing, wheezing, or persistent coughing, that’s an emergency-level concern.

Respiratory issues in cats can escalate quickly and might indicate asthma, heart disease, or respiratory infections.

When to Call the Vet

A good rule of thumb is: when in doubt, call your vet. They’d much rather you check in about something small than wait until it’s serious.

Call immediately if you notice:

• Difficulty breathing
• Inability to urinate (especially in male cats)
• Seizures or collapse
• Severe vomiting or diarrhea
• Visible injuries or bleeding
• Lethargy or unresponsiveness

For less urgent concerns, still reach out within 24 hours if symptoms persist.

The Bottom Line

How to know if your cat is sick really comes down to knowing what’s normal for your cat. Spend time observing their habits, routines, and personality. Take mental notes of how much they typically eat, drink, and use the litter box. That way, when something changes, you’ll catch it early.

And remember—you’re not being an overprotective cat parent by being vigilant. You’re being a good one! Our cats depend on us to be their voice when they’re not feeling their best.

Has your cat ever hidden an illness from you? What signs finally tipped you off? Share your experience in the comments below.

Also read:
How to Protect Your Pets from Household Poisoning Risks
Here’s How to Choose a Great Pet Name

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