Cats are absolute pros at hiding their pain—it’s a hardwired survival instinct that can make life difficult for us owners. By the time you notice something is wrong, the issue might already be advanced. Learning to spot the early warning signs of common ailments is one of the most important things you can do for your pet. This guide breaks down the usual suspects, what to look for, and exactly when you need to call the vet.
Common Cat Health Problems: Spotting the Signs and Knowing When to Call the Vet
Author: Dr. Sarah Mitchell, DVM · Published: 2026 · Updated: July 17, 2026 · Reading time: ~10 minutes
Cats are masters of disguise. By the time they "look sick" to a casual observer, they've usually been unwell for days. The trick is not to wait for dramatic symptoms — it's to learn what small, day-to-day changes mean, and to know which ones warrant urgent action. This guide walks you through common cat health problems, how to recognize them at each stage, and exactly when each one crosses the line into "call the vet right now."
How to spot that something is wrong
Cats communicate illness through behavior changes more than dramatic symptoms. Watch for:
- Eating or drinking more or less than usual
- Litter box changes (size, number, frequency, color, consistency)
- Hiding more than usual or being unusually clingy
- Coat changes — dull, matted, oily, or unkempt
- Weight loss, especially gradual — many owners don't notice until it's substantial
- Drop in energy or activity; reluctance to jump or play
- Vomiting that's more than occasional hairball
- New behavioral habits: avoiding the litter box, sleeping in unusual places
The two highest-yield things a cat owner can do:
- Weigh your cat regularly. A home scale you can zero with a container works well. Even a 200-gram change in a cat is meaningful.
- Notice what "normal" looks like. You can't recognize abnormal until you have a clear baseline.
The most common cat health problems — and what they look like
1. Vomiting (chronic and acute)
Cats vomit for many reasons. The key is distinguishing a hairball from something more serious.
Common causes:
- Hairballs (especially long-haired cats during shedding season)
- Dietary indiscretion (eating something they shouldn't)
- Inflammatory bowel disease or low-grade GI lymphoma
- Pancreatitis
- Foreign body obstruction
- Kidney disease
- Hyperthyroidism
When to call the vet:
- Repeated vomiting (more than two episodes in 12 hours)
- Vomit with blood or that looks like coffee grounds
- Vomiting combined with lethargy, weight loss, or refusal to eat
- A cat who is also straining or unable to keep water down
- Suspected toxin ingestion
2. Diarrhea
Most short bouts of diarrhea are self-limiting, but persistent or severe cases need attention.
Common causes:
- Dietary change or food sensitivity
- Parasites (especially in kittens or outdoor cats)
- Inflammatory bowel disease
- Infections
- Stress-related colitis
When to call the vet:
- Diarrhea with blood or mucus
- Diarrhea combined with vomiting, lethargy, or dehydration
- A kitten who has diarrhea (kittens dehydrate fast)
- Any cat not vaccinated who develops diarrhea
3. Lower urinary tract disease (LUTD/FIC/blocked cats)
Often called feline idiopathic cystitis (FIC) when no clear cause is found.
Signs:
- Straining in the litter box with little or no urine
- Crying while urinating
- Frequent small urinations outside the box
- Blood in urine
- Excessive licking around the rear
When to call the vet:
- A male cat who is straining and not producing urine is an EMERGENCY. According to the [Merck Veterinary Manual}(https://www.merckvetmanual.com/urinary-system/urolithiasis-in-small-animals/urethral-obstruction-in-small-animals), a complete obstruction can cause uremia within 36–48 hours and may lead to coma and death at approximately 72 hours.
This is a high-stakes emergency. If you have a male cat and suspect he can't urinate, do not wait for morning. Go to emergency now.
4. Dental disease
Most cats over three have some degree of dental disease.
Signs:
- Bad breath
- Yellow or brown tartar on teeth
- Drooling, especially with blood-tinged saliva
- Dropping food or chewing on one side
- Pawing at the mouth
- Decreased appetite, especially for hard food
Care:
- Routine brushing with enzymatic cat toothpaste is the single most effective prevention
- Annual veterinary dental exams; cleaning under anesthesia as recommended
Dental disease is also linked to kidney, heart, and liver disease in older cats — it's not "just teeth."
5. Kidney disease
Common in older cats (over 10) but can occur earlier.
Signs:
- Increased thirst and urination
- Weight loss
- Poor appetite
- Lethargy
- Sometimes vomiting or constipation
- Subtle coat changes
Care:
- Bloodwork (BUN, creatinine, SDMA) and urinalysis for diagnosis
- A veterinarian may recommend a therapeutic renal diet to support quality of life and slow disease progression; [International Cat Care}(https://icatcare.org/articles/chronic-kidney-disease-ckd-in-cats) emphasizes choosing an appropriate diet based on the individual cat’s condition
- Subcutaneous fluids at home may be recommended for some stable chronic kidney disease cats
- Blood pressure monitoring and management
Because signs can be subtle, regular veterinary exams and testing can help identify kidney disease before it becomes advanced.
6. Hyperthyroidism
Most common in cats over 8.
Signs:
- Weight loss despite a ravenous appetite
- Restlessness or hyperactivity
- Vomiting or diarrhea
- Increased thirst and urination
- Unkempt coat
- Sometimes a palpable thyroid nodule in the neck
Care:
- Bloodwork (T4, sometimes full thyroid panel)
- Treatments: daily oral medication (methimazole), prescription diet (in some cases), radioactive iodine therapy (often curative), or surgical thyroidectomy
Hyperthyroidism is highly treatable, and most cats respond beautifully.
7. Diabetes
Increasingly common, especially in overweight middle-aged cats.
Signs:
- Increased thirst and urination
- Weight loss despite eating well
- Increased appetite initially; sometimes decreased appetite in advanced disease
- Lethargy or weakness
- Walking with hind legs flat ("plantigrade stance") in some cats
Care:
- Bloodwork and urinalysis (glucose)
- Insulin and an individualized diet plan
- Glargine U-100 and protamine zinc insulin are common options with an acceptable duration of action in cats, according to the [2026 AAHA Diabetes Management Guidelines}(https://www.aaha.org/resources/2026-aaha-diabetes-management-guidelines-for-cats/section-7-insulin-treatment-and-monitoring/)
- The [AAHA dietary guidelines}(https://www.aaha.org/resources/2026-aaha-diabetes-management-guidelines-for-cats/section-8-dietary-management/) state that many diabetic cats benefit from a high-protein, reduced-carbohydrate diet, while emphasizing reliable food intake and each patient’s individual needs
- Home glucose monitoring may be part of a veterinarian-directed management plan
- Some cats achieve remission, although remission is not possible or appropriate for every patient
8. Skin problems and allergies
Common signs:
- Overgrooming to bald patches, especially on the belly, inner thighs, and forelimbs
- Small scabs or crusty lesions ("miliary dermatitis")
- Itching, especially around the head and neck
- Ear scratching, head shaking
Common causes:
- Flea allergy dermatitis (a single flea can trigger an allergic response)
- Environmental allergies (dust, pollen)
- Food allergies
- Fungal infections (ringworm)
- Mites
Care:
- Year-round flea prevention
- Diet trial for food allergies
- Cytology or skin scrape to look for infections
- Antihistamines or targeted treatments in stubborn cases
9. Eye issues
Cats' eyes rarely show obvious discharge without good reason.
Common signs and concerns:
- Persistent discharge (clear, yellow, or green)
- Squinting or closed eye
- Cloudy cornea or changed eye appearance
- Visible third eyelid (often a sign of systemic illness)
- Bulging eye or sudden swelling
Care:
- Many eye issues progress fast and can threaten vision; same-day vet visits are often warranted
- Corneal ulcers, uveitis, and glaucoma are emergencies
10. Respiratory infections
Most often viral (feline herpesvirus and calicivirus are most common).
Signs:
- Sneezing, runny eyes or nose
- Decreased appetite (often because they can't smell the food)
- Fever, lethargy
- Eye or nose discharge that changes from clear to colored
Care:
- Supportive care: humidity, warmed smelly food, fluids, eye drops if prescribed
- Antibiotics if secondary bacterial infection is suspected
- L-lysine is not recommended as an effective prevention or treatment for feline herpesvirus; a [systematic review indexed by PubMed}(https://pubmed.ncbi.nlm.nih.gov/26573523/) found no evidence of efficacy
- Stress and illness can reactivate herpesvirus throughout a cat's life
11. Heart disease
Hypertrophic cardiomyopathy (HCM) is the most common form.
Signs:
- Often subtle: decreased activity, labored breathing, hiding
- Open-mouth breathing or panting in cats is a critical sign
- Sudden hind-leg paralysis (in a form called aortic thromboembolism, or "ATE")
- Fainting episodes
Care:
- Echocardiogram (ultrasound of the heart) is the gold standard
- Many HCM cats live normal or near-normal lives on medication
- Some breeds (Maine Coon, Ragdoll, British Shorthair) have genetic testing available
Cats with HCM need regular re-checks, and any sign of breathing trouble warrants an immediate vet visit.
12. Cancer
Lymphoma is the most common, but other cancers — mast cell tumors, squamous cell carcinoma, mammary carcinoma, injection-site sarcomas — occur as well.
General signs vary by site:
- Lumps or masses that grow or change
- Unexplained weight loss
- Decreased appetite or vomiting
- Difficulty eating (oral tumors)
- Lameness or swelling
- Non-healing wounds
Care: Early evaluation, biopsy, imaging, and discussion with an oncologist if available.
13. Toxins and household hazards
Cats are uniquely sensitive to several common items:
- Lilies (Lilium and Hemerocallis species) — even a small exposure to pollen, leaf, or vase water can cause acute kidney injury
- Acetaminophen (Tylenol) — toxic at small doses
- Antifreeze (ethylene glycol) — sweet but deadly
- Many essential oils — including tea tree, citrus, wintergreen, pennyroyal
- Some human foods — onions, garlic, grapes, raisins
- Certain houseplants — pothos, philodendrons, lilies
- Strings, ribbons, rubber bands — chewing can cause life-threatening intestinal obstruction
If you suspect any exposure, call the [ASPCA Animal Poison Control Center}(https://www.aspca.org/pet-care/animal-poison-control) at 888-426-4435 or the [Pet Poison Helpline}(https://www.petpoisonhelpline.com/) at 855-764-7661, then contact your veterinarian or emergency clinic. Bring the product packaging if it is safe to do so.
Triage: when each sign means "today, not tomorrow"
| Sign | Urgency |
|---|---|
| Open-mouth breathing | ER now |
| Unresponsive or limp cat | ER now |
| Suspected toxin | ER now |
| Straining male cat not producing urine | ER now |
| Trauma (fall, animal bite, vehicle) | ER now |
| Seizure | ER now |
| Eye injury or sudden blindness | ER today |
| Bleeding that doesn't stop | ER today |
| Repeated vomiting in short window | Same day |
| New weight loss of >5% in a short time | Within 24–48 hours |
| Persistent lethargy or appetite loss | Within 24–48 hours |
| Mild stool changes without other signs | Often monitor briefly, call if persists |
The most important things you can do at home
- Annual bloodwork starting at age 7 catches many diseases early.
- Weigh monthly. Keep a small log.
- Maintain vaccination and parasite prevention.
- Provide fresh water in multiple locations to encourage drinking — kidney and urinary tract health benefit significantly.
- Feed a complete and balanced diet appropriate for your cat’s age and health, unless a vet recommends otherwise.
- Know your emergency clinic before you need one. Have the address and number saved in your phone.
Frequently asked questions
How often should my cat see the vet?
Healthy adults: yearly, ideally with bloodwork. Cats over 7: every 6 months is safer — disease progresses fast in older cats. Kittens: following the kitten vaccine schedule, generally 3–4 visits in the first year.
Do indoor cats need vaccines?
Yes — at minimum rabies (required by law in many jurisdictions) and a combination distemper (FVRCP) vaccine. Lifestyle-based options like FeLV and FIV for outdoor or multi-cat homes should be discussed with your vet.
Is dry food bad for cats?
Not "bad" per se. The right diet depends on your cat’s age, body condition, preferences, and medical needs. Many cats do well on wet food, dry food, or a combination. Discuss your cat’s specific nutritional needs with your veterinarian.
When is the right time to consider euthanasia?
This is a personal decision, often discussed with your vet. Quality-of-life scales (HHHHHMM) and individual conversations help. Many owners and vets aim for "more good days than bad" as a guiding principle. There is no single right moment — only the moment that's right for your cat and your family.
Should I get pet insurance?
Pet insurance generally gives you more treatment options in an emergency or with a serious diagnosis. It rarely covers pre-existing conditions, so enrolling while your cat is young and healthy is most valuable. Compare waiting periods, exclusions, and lifetime payout caps.
About the Author
Dr. Sarah Mitchell, DVM, is a contributing veterinarian specializing in feline preventive medicine. She is a small-animal veterinarian with a clinical focus on feline preventive care, behavior, and household safety. Her articles translate clinical protocols and peer-reviewed research into practical guidance that cat owners can use daily.
For personalized advice for your cat, consult a licensed veterinarian in your area.