How to Tell If Cat Is Sick: 8 Warning Signs

Cats are masters of hiding pain. It’s an instinct baked in from their wild ancestors — showing weakness invites predators. That makes spotting illness tricky, especially for new cat owners. The signs on this list are the ones veterinarians flag most often as early warnings that something’s wrong. Some are subtle. Some are obvious once you know what to look for. All of them are worth acting on.

This list focuses on changes — shifts from your cat’s normal baseline — because that’s what actually matters. A cat who sleeps 16 hours a day isn’t necessarily sick. A cat who suddenly sleeps 16 hours and used to be active? That’s a different story.

A useful habit: spend 30 seconds observing your cat each morning. Eating? Moving normally? Coat look right? This quick mental check-in builds the baseline that makes changes visible before they escalate.

1. Changes in Eating or Drinking Habits

A healthy cat has a fairly consistent appetite. If yours suddenly stops eating, picks at food, or refuses a meal they normally love, pay attention — cats who go without food for more than 48 hours are at risk for hepatic lipidosis (fatty liver disease), a serious condition that develops faster in cats than in any other domestic animal.

The reverse is also a red flag. A cat who suddenly eats significantly more — or drinks noticeably more water — may be dealing with conditions like diabetes, hyperthyroidism, or kidney disease. Kidney disease affects roughly 1 in 3 cats over the age of 10, and increased thirst is often one of the first signs owners notice.

Keep a rough mental log of your cat’s daily eating and drinking habits. You don’t need to measure ounces, but you should notice if the water bowl is emptier than usual or if food is going untouched by the end of the day.

Signs to watch for:

• Leaving food in the bowl for more than a few hours (for a cat who normally finishes meals)
• Drinking from multiple sources or the tap frequently
• Weight loss alongside increased appetite
• Drooling, pawing at the mouth, or dropping food while eating (possible dental pain)

2. Hiding or Withdrawing from the Family

If your normally social cat suddenly disappears under the bed for most of the day, that’s a signal. Cats instinctively retreat when they feel unwell — it’s a protective behavior rooted in survival. They’re not being moody. They’re telling you something feels off.

This is one of the most commonly missed signs because owners chalk it up to personality. “My cat’s just shy.” But hiding that’s out of character — especially combined with any other symptom — deserves attention.

There’s a difference between a cat who retreats to a favorite quiet spot for a few hours and one who stays hidden all day, refuses food where they’re lying, and doesn’t come out for their usual triggers (the sound of the can opener, your footsteps at dinner time). That second pattern is the one to act on.

Don’t force interaction. Instead, check on them gently and look for other signs like shallow breathing, visible discomfort, or reluctance to move.

3. Litter Box Changes

The litter box is one of your best diagnostic tools. Changes in frequency, consistency, or behavior around the box can point to a range of health issues.

Straining to urinate — especially in male cats — is a medical emergency. A blocked urethra can become fatal within 24–48 hours. If your cat is squatting in the box repeatedly with little or no output, go to the vet immediately. Don’t wait until morning. Don’t call and leave a message. Go.

Diarrhea lasting more than 24 hours, blood in the stool or urine, or accidents outside the box are all worth a vet call. So is going to the box more often than usual, which can indicate a urinary tract infection. Female cats are more prone to UTIs; male cats are more prone to blockages — both need prompt attention.

Common litter box red flags:

• Straining with no urine output (emergency)
• Blood in urine or stool
• Soft, watery, or unusually dark stools
• Urinating or defecating outside the litter box
• Crying or vocalizing while using the box
• Sudden increase in frequency of visits

4. Vomiting or Diarrhea

Cats vomit occasionally — hairballs happen. But frequent vomiting, especially with blood, bile, or undigested food, isn’t normal. Vomiting more than once or twice a week, or multiple times in a single day, points to something that needs investigating.

Diarrhea for more than 24 hours can quickly lead to dehydration, especially in kittens and older cats. If the stool is black or tarry, that can indicate bleeding in the upper digestive tract and needs immediate attention.

Don’t confuse regurgitation with vomiting. Regurgitation happens almost immediately after eating, often with undigested food in a tube shape. Vomiting involves heaving and brings up partially digested food or bile. Both matter, but they point to different issues — regurgitation often signals esophageal problems or eating too fast, while vomiting can indicate anything from gastritis to pancreatitis.

5. Lethargy or Unusual Tiredness

Cats sleep a lot — 12 to 16 hours is completely normal. The issue is when a cat’s energy level drops noticeably below their own personal baseline.

A cat who used to greet you at the door and now barely lifts their head, or one who’s skipping their usual play sessions and lying flat instead of curled up comfortably — that’s a change worth noting. Lethargy is one of the most generic signs of illness, which means it can point to almost anything from anemia to infection to organ disease.

Pay particular attention to how they’re resting. A sick cat often lies stretched out flat rather than curled — this can indicate they’re trying to relieve internal discomfort. A cat who normally sleeps in your lap but is now isolating in corners is showing you two symptoms at once: lethargy and withdrawal.

Pair lethargy with other signs (not eating, hiding, changes in breathing) to help your vet narrow down the cause. On its own, it still warrants a call if it persists for more than a day or two.

6. Changes in Coat and Grooming

A healthy cat’s coat is smooth, clean, and relatively free of mats. Cats spend a significant chunk of their day grooming — it’s both hygiene and comfort behavior. When that changes, it usually means something’s wrong.

Over-grooming (excessive licking, pulling fur, creating bald patches) can signal skin conditions, parasites like fleas, or anxiety and stress. It can also point to pain — cats sometimes focus grooming on a specific area that hurts, particularly joints affected by arthritis or spots with internal discomfort beneath the skin.

Under-grooming is more commonly tied to physical illness. A cat who stops grooming looks unkempt — dull coat, matted fur, greasy appearance. This often happens with arthritis (it hurts to reach certain spots), obesity, dental pain, or systemic illness that drains their energy. Senior cats with joint issues are especially prone to matting along the back and base of the tail, areas they can no longer comfortably reach.

What to look for:

• Bald patches or thinning fur
• Greasy, dull, or matted coat
• Excessive scratching or licking one area
• Flaky skin or visible sores
• Coat that looks “off” compared to their usual condition

7. Respiratory Changes

Any change in breathing should be taken seriously. Cats are obligate nose-breathers — a cat breathing through their mouth (unless they’re extremely hot or just exerted themselves) is not okay. Open-mouth breathing is a potential emergency.

Watch for labored breathing, rapid shallow breaths, or visible effort in the chest and belly area. A resting respiratory rate above 30 breaths per minute is considered abnormal. If you’re unsure, count chest rises for 30 seconds and double it — anything over 30 warrants immediate attention.

Wheezing, sneezing more than usual, or nasal discharge can point to upper respiratory infections, which are highly contagious between cats. If your cat is breathing with their elbows out, neck extended, or belly heaving — don’t wait. This is a sign of respiratory distress and needs immediate veterinary care.

8. Eye, Ear, or Mouth Issues

These are the areas most people overlook during a casual check, but they’re full of useful information.

Eyes: Healthy cat eyes are clear and bright. Cloudiness, excessive discharge, redness, squinting, or a visible third eyelid (the pale membrane in the inner corner) are all signs of illness or injury. Sudden changes in pupil size or asymmetry can indicate neurological problems and warrant same-day evaluation.

Ears: Frequent head shaking, scratching at ears, dark discharge, or a strong odor can mean ear mites, infection, or yeast. Both ear mites and infections need treatment — they don’t resolve on their own, and untreated infections can cause permanent hearing damage.

Mouth: Bad breath in cats isn’t normal, and it’s not something to write off as just “cat breath.” A strong odor can indicate dental disease, kidney problems, or infection. Studies show over 70% of cats develop signs of dental disease by age 3, yet most go untreated because owners don’t recognize the early signs. If your cat is pawing at their mouth, drooling, or avoiding hard food, dental pain is the likely cause. Oral health issues are among the most undertreated problems in cats — and one of the most preventable.

Quick Reference: Symptoms and Urgency

What to Do If You Spot These Signs

Don’t wait to see if it gets better on its own — especially with cats. Because they hide discomfort so effectively, by the time symptoms become obvious, the condition may already be progressing. A same-day or next-day vet visit for anything more than the mildest symptoms is always the right call.

When you call the vet, be specific. Note when the symptom started, how often it’s occurring, and any other changes you’ve noticed — even small ones. If you can, take a short video of the behavior. A 30-second clip of abnormal breathing, limping, or litter box behavior gives the vet far more information than a verbal description alone.

A few practical habits that help catch problems early:

• Run your hands over your cat weekly — feel for lumps, sore spots, or changes in weight
• Glance at the litter box daily before scooping
• Notice your cat’s energy and appetite as part of your daily routine
• Schedule annual vet checkups (twice yearly for cats over 7)
• Keep a simple note on your phone with your cat’s normal weight — sudden loss of half a pound in a small cat is clinically significant

The cats who get caught early — before a UTI becomes a blockage, before weight loss becomes severe — have far better outcomes. Your observation is genuinely one of the most powerful health tools your cat has.

If anything on this list matches what you’re seeing right now, trust your gut and call your vet. You know your cat. If something feels off, it probably is.

Frequently Asked Questions

Why is it hard to tell if a cat is sick?

Cats instinctively hide pain as a survival mechanism from their wild ancestors—showing weakness invites predators. This makes spotting illness tricky, especially for new cat owners.

What happens if a cat doesn’t eat for 48 hours?

Cats that go without food for more than 48 hours risk developing hepatic lipidosis (fatty liver disease), a serious condition that develops faster in cats than in any other domestic animal.

What does increased drinking in cats indicate?

Sudden increases in thirst may signal diabetes, hyperthyroidism, or kidney disease. Kidney disease affects roughly 1 in 3 cats over age 10, with increased thirst often being one of the first noticeable signs.