How to Tell If Your Cat Is Sick: 10 Warning Signs

About this guide: Written by cat parent and Pawfect Cat Care founder Hicham Aouladi and fact-checked using reputable veterinary sources. For educational purposes only — not a substitute for professional veterinary advice.

Worried cat owner comforting an indoor tabby on a beige sofa — early warning signs of a sick cat and when to see the vet

I’ve had those “is something wrong… or am I overthinking it?” moments with my own cat—when everything looks normal, but the vibe is off. Maybe they skip breakfast, hide a little longer, or the litter box looks different.

Cats are experts at masking discomfort, so small changes matter. Below you’ll find 10 common warning signs, the red flags where you shouldn’t wait, and a simple tracking checklist that makes it much easier to explain what you’re seeing to your vet.

1) Why early detection matters

Cats evolved to hide weakness. In the wild, looking “fine” helped them stay safe—so today your indoor cat might still act normal while quietly feeling awful. That’s why early illness often shows up as little shifts: less play, more hiding, a coat that looks dull, or a small change in the litter box.

When you catch those changes early, your vet has a better shot at diagnosing the real issue quickly—and you can often prevent dehydration, pain spirals, and complications like fatty liver disease (which can happen when cats stop eating).

Quick check-in: If something feels “off,” trust that instinct. You don’t need a perfect diagnosis—just a clear pattern and a next step.

2) 10 warning signs to watch (and what they may mean)

1. Changes in appetite

A cat who suddenly stops eating, eats much less, or acts hungry but walks away can be dealing with nausea, dental pain, stress, kidney/liver issues, mouth ulcers, or other problems. If an adult cat refuses food for 24 hours (or a kitten refuses for 12 hours), call your vet.

2. Sudden weight loss or gain

Weight changes are a big clue—especially when they don’t match the appetite. Fast weight loss with a normal or bigger appetite can point toward conditions like hyperthyroidism or diabetes. Sudden “weight gain” can sometimes be fluid retention (not just treats).

3. Vomiting or diarrhea

A hairball here and there can happen, but repeated vomiting or watery diarrhea isn’t “normal cat stuff.” Ongoing GI upset dehydrates cats quickly. If you see blood (or black, tarry stool), that’s urgent.

4. Lethargy or weakness

Concerned owner comforting a lethargic indoor tabby cat on a sofa — early sign of illness and when to see the vet

If your usually curious cat suddenly sleeps all day, skips playtime, hides, or stops jumping up to favorite spots, assume something is bothering them—pain, fever, infection, anemia, or another medical issue. Collapse, wobbliness, or “can’t get up” weakness needs urgent care.

5. Changes in grooming

Over-grooming (bald patches, scabs) can be allergies, fleas/mites, pain, or stress. Under-grooming (greasy coat, mats) is common with arthritis, dental pain, obesity, or systemic illness.

6. Breathing problems

Fast breathing, wheezing, coughing, or open-mouth breathing at rest can be serious (asthma, infection, heart issues). If breathing looks hard or the gums look pale/blue, treat it as an emergency and go in.

7. Increased thirst and urination

If water bowls empty faster and litter clumps are bigger, think kidneys, diabetes, or hyperthyroidism. On the other side: tiny frequent pees, straining, crying in the box, or licking the genitals can signal a urinary blockage, especially in male cats—this is an emergency.

8. Behavioral changes

Cats don’t “act weird for no reason.” New aggression, clinginess, hiding, or avoiding favorite perches often points to pain or stress. With seniors, new nighttime yowling or confusion can sometimes go along with blood pressure or cognitive changes. (If anxiety might be part of it, see: Cat Anxiety: Signs & Solutions.)

9. Bad breath or drooling

Bad breath plus pawing at the mouth often means dental disease, abscess, or ulcers. Breath that smells like ammonia can happen with kidney disease. Sweet/acetone breath can be dangerous in uncontrolled diabetes—both need prompt vet attention.

10. Limping or mobility changes

Hesitating to jump, stiff walking, slipping, or a sudden limp can be arthritis, injury, or neurological issues. A dangling limb, sudden paralysis, or cold painful back legs is urgent—go in.

3) Red-flag signs (go now, not later)

  • Straining to urinate, producing only drops, or crying in the litter box (especially male cats).
  • Open-mouth breathing, labored breathing, blue/gray gums, or obvious breathing effort.
  • Repeated vomiting with lethargy, or any blood/coffee-ground material.
  • Suspected ingestion of string, needles, batteries, human medications, lilies, or unknown toxins.
  • Refusal to eat >24h (or >12h for kittens) or refusal to drink plus dry/sticky gums.
  • Seizure, collapse, sudden severe pain, or sudden paralysis.

4) What to track at home (the simple stuff that helps your vet)

You don’t need fancy gear. You just need consistency. A few quick notes can reveal a pattern you’d miss otherwise. And when you call the clinic, you’ll sound calm and clear—because you’ll have real details.

  • Appetite: what you offered and how much was eaten.
  • Water: bowl refills; bigger/smaller urine clumps than usual.
  • Energy & behavior: play level, hiding, mood shifts, extra vocalizing.
  • Litter box: diarrhea/constipation, blood/mucus, straining.
  • Breathing: count at rest (30 seconds × 2). Many calm cats land around 16–30 breaths/min.
  • Weight: a weekly scale check catches slow changes early.

Simple daily health journal (takes 60 seconds)

FieldWhat to note
MealsAmount eaten (% of usual) + interest in food
WaterBowl refills / fountain use; any change in thirst?
LitterPee count/clump size; stool consistency/shape
EnergyPlay interest, hiding, moving/jumping
Coat/GroomingShiny vs dull/greasy; mats; over/under-grooming
NotesCough/sneeze, breath smell, odd behaviors (video if needed)

Body condition & hydration quick checks

  • Ribs: you should feel them with a thin fat cover (not sharp, not buried).
  • Waist: a gentle tuck behind the ribs when viewed from above.
  • Gums: moist is normal; tacky/dry can hint dehydration.
  • Big picture: one odd moment isn’t always a crisis—patterns are what matter.

Optional tools (nice, not required)

  • Baby/pet scale: weekly weigh-ins catch trends early.
  • Litter tracking: helps you notice frequency/volume changes.
  • Auto-feeder logs: useful if you’re away and need appetite data.

5) Smart triage (what’s urgent vs. what can wait)

Same-day emergency: breathing trouble, suspected urinary blockage, repeated vomiting with lethargy, suspected toxin, major trauma, collapse, neurologic signs, uncontrolled bleeding.

Urgent appointment (24–48 hours): new appetite loss, ongoing diarrhea, limping, fever, painful mouth, big thirst/urination change, eye squint/discharge, suspected dental pain.

Monitor + call if it repeats: one vomit with normal behavior, mild soft stool under 24 hours, brief picky eating if your cat is otherwise bright.

Real-life scenarios (fast triage)

Case 1: “He’s peeing often, tiny clumps.”
Call your vet today—urgent if a male cat is straining or crying in the box.

Case 2: “She’s eating more but losing weight.”
Book bloodwork (common causes include hyperthyroidism or diabetes). Track weight + water intake until the visit.

Case 3: “He’s hiding and the coat looks greasy.”
Often pain, dental issues, fever, or arthritis. If it lasts 24–48h or appetite drops, schedule urgent care.

6) How to prepare for the vet visit (so you get answers faster)

Cat at the vet being examined while the owner keeps a simple symptom log
  • Record short videos of breathing, gait, litter-box straining, or unusual behavior.
  • Bring a fresh stool sample (within 6–8 hours) in a sealed bag if GI issues are involved.
  • Write a quick list: meds/supplements, diet changes, litter changes, recent stressors.
  • Carrier calm: towel, cover the carrier in the car, and consider pheromone spray 10–15 minutes before leaving.

If you want a ready checklist of supplies, see: Cat First-Aid Kit 2025.

7) Symptom-by-symptom guide (what it often points to)

  • Appetite down: dental disease, nausea (kidneys/liver/pancreas), pain, GI disease.
  • Eating more: hyperthyroidism, diabetes (often with weight loss), malabsorption.
  • Drinking/peeing more: diabetes, kidney disease, hyperthyroidism, medication effects.
  • Vomiting/diarrhea: diet change, parasites, IBD, pancreatitis, foreign body, toxins.
  • Lethargy: fever, anemia, pain, metabolic disease, infection.
  • Bad breath/drooling: periodontal disease, tooth resorption, oral ulcers.
  • Limping/stiffness: arthritis, injury, nail bed issues; sudden cold painful back legs = emergency.
  • Behavior shifts: pain, blood pressure issues, cognitive change, anxiety — see Cat Anxiety: Signs & Solutions.

Quick guide: symptoms that often cluster together

ConditionEarly cluesNext steps
Dental disease Bad breath, drooling, pawing at mouth, dropping kibble Book a dental exam; softer food can help until seen
Kidney disease More thirst/urination, gradual weight loss, dull coat Vet visit for blood/urine tests; prioritize hydration
Diabetes Big appetite + weight loss, lethargy, messy coat Vet testing; track water + litter clumps
Hyperthyroidism Weight loss, louder meowing, vomiting, restlessness Blood test (T4); book an appointment
Urinary issues Tiny frequent pees, straining, licking genitals, accidents Urgent for males; vet same-day if straining

8) Home care you can do (without masking problems)

The goal at home is comfort and support—not “DIY treatment.” If symptoms are significant or worsening, it’s always safer to call your clinic. That said, these basics can help while you’re monitoring or waiting for an appointment:

  • Hydration: offer wet food; add warm water or low-sodium broth (no onion/garlic).
  • Quiet recovery zone: soft bedding + easy access to litter, food, and water.
  • Gentle grooming: help under-groomers, and check for mats/tender areas.
  • Never give human meds: ibuprofen and acetaminophen can be toxic to cats.
  • Don’t “wait it out” if appetite is off—cats can develop fatty liver after short periods without food.

9) Senior-specific watchlist

With older cats, changes can be subtle and gradual. Keep an eye on thirst, weight, muscle loss along the spine, constipation, and jumping reluctance. If your cat is 7+ (and especially 10+), routine bloodwork and blood pressure checks can catch issues before they become emergencies.

Quick home wins: low-entry litter boxes, non-slip rugs, and steps to favorite spots can make a big difference fast.

10) Kittens: extra caution

Kittens dehydrate faster and can crash quickly. Diarrhea, vomiting, or a missed meal can turn serious within hours. If a kitten seems listless, refuses food, or has ongoing diarrhea, call your vet the same day.

11) At-home monitoring template (copy/paste)

  • Day/date and time window
  • Food offered / amount eaten (wet/dry/treats)
  • Water refills / urine clump sizes
  • Poops (consistency, color, blood/mucus)
  • Energy/behavior notes (hiding, play, vocalization)
  • Breathing rate at rest (breaths/min)
  • Notes/questions for the vet

12) FAQs (quick answers)

My cat vomited once but is acting normal—do I need a vet?
One isolated vomit in a bright, eating cat can sometimes be watched. If vomiting repeats, energy drops, appetite changes, or you see blood, book a visit.

How long can I wait if my cat isn’t eating?
Don’t wait. If an adult skips more than one meal, call your vet. For kittens, any missed meal is worth a same-day call.

Cough vs. hairball—how can I tell?
It’s hard without a video. Coughing can be asthma or heart disease, while hairball retching looks different. Record a short clip and show your vet.

What should I bring to the clinic?
Photos/videos, a fresh stool sample if relevant, a medication list, and photos of the food label (or the bag/can).

13) Prevention that pays off

  • Wellness visits: yearly for adults; twice yearly for seniors or chronic issues.
  • Dental checks: dental pain causes appetite and behavior changes fast.
  • Gradual food changes: switch foods over 7–10 days.
  • Parasite prevention: follow vet guidance for your area and lifestyle.
  • Low-stress home: routine, vertical space, and daily play.

During hot spells, hydration matters even more—see: Heatwave Safety for Indoor Cats.

14) When to call the vet now (quick list)

Breathing trouble • Straining to urinate • Suspected toxin/string ingestion • Repeated vomiting + lethargy • Not eating (24h adults; 12h kittens) • Collapse or seizures • Pale/blue/yellow gums • Sudden painful, cold back legs

15) Bringing it together

The goal isn’t to panic over every hairball—it’s to notice when your cat’s “normal” changes. You know your cat better than anyone. Track what you see, act early on red flags, and work with your veterinarian. That simple routine—observe, log, call—catches problems while they’re still easier to treat and keeps your cat comfortable.

References

Disclaimer

This article is educational and not a substitute for veterinary care. If you notice any red-flag signs, contact your veterinarian or an emergency clinic immediately. Full site disclaimer: Pawfect Cat Care — Disclaimer.

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