One of the hardest parts of being a pet owner is that your animal can’t tell you when they’re not feeling well. Unlike humans, pets instinctively hide signs of illness — a survival mechanism inherited from their wild ancestors, who would have been vulnerable to predators if they showed weakness.
This means that by the time a pet looks obviously unwell, they may have been struggling for a while already. Learning to recognize the early and subtle signs that something is off is one of the most valuable skills you can develop as a pet owner — and it can genuinely save your animal’s life.
Here are 15 warning signs to watch for, what they might indicate, and when to call the vet.
1. Changes in Eating or Drinking Habits
A sudden loss of appetite — or conversely, a dramatic increase in hunger or thirst — is one of the most reliable early indicators that something is wrong. Missing one meal occasionally isn’t cause for panic, but if your pet refuses food for more than 24–48 hours, it warrants a call to your veterinarian.
Increased thirst and urination together can indicate kidney disease, diabetes, or Cushing’s disease in both dogs and cats. Decreased water intake combined with lethargy can signal dehydration or organ problems.
2. Unexplained Weight Loss or Gain
Gradual weight changes can be easy to miss, especially in long-haired pets. Get in the habit of running your hands along your pet’s ribs and spine regularly — you should be able to feel the ribs without pressing hard, but not see them prominently.
Unexplained weight loss in cats is particularly concerning and can indicate hyperthyroidism, diabetes, kidney disease, cancer, or inflammatory bowel disease. Rapid weight gain, especially with a distended abdomen, can signal fluid accumulation, organ enlargement, or other serious conditions.
3. Lethargy or Unusual Tiredness
All pets have off days. But if your normally energetic dog or playful cat suddenly becomes withdrawn, uninterested in activities they usually enjoy, or spends significantly more time sleeping than usual, it’s worth paying attention.
Lethargy is one of the most common but non-specific signs of illness — it accompanies everything from mild infections to serious systemic disease. Combined with any other symptoms on this list, it becomes more significant.
4. Vomiting or Diarrhea
Occasional vomiting or a single episode of loose stools isn’t automatically cause for alarm — pets eat things they shouldn’t, and minor digestive upsets happen. However, the following warrant prompt veterinary attention:
- Vomiting or diarrhea that persists for more than 24 hours
- Blood in vomit or stool
- Vomiting combined with lethargy, loss of appetite, or abdominal pain
- Signs of dehydration (sunken eyes, dry gums, skin that doesn’t spring back when gently pinched)
- Suspected ingestion of a toxic substance
In cats, frequent vomiting is never truly “normal” — the common belief that cats vomit hairballs regularly is often used to dismiss symptoms that deserve investigation.
5. Difficulty Breathing
Any labored breathing, wheezing, persistent coughing, or open-mouth breathing in cats (which is almost always abnormal) is a potential emergency. Respiratory distress can indicate heart disease, asthma, pneumonia, pleural effusion (fluid around the lungs), or airway obstruction.
If your pet is breathing with visible effort, breathing rapidly at rest, or using their abdominal muscles to breathe, seek emergency veterinary care immediately.
6. Changes in Urination
Straining to urinate, crying out while urinating, urinating more or less frequently than usual, blood in the urine, or accidents in a previously house-trained pet all indicate a problem that needs veterinary attention.
Urinary blockage — more common in male cats — is a life-threatening emergency. A cat that is straining in the litter box and producing little or no urine needs emergency care within hours, not days.
7. Limping or Difficulty Moving
Sudden lameness after exercise may indicate a sprain or strain. But persistent limping, difficulty rising from a resting position, reluctance to jump or climb stairs, or obvious pain when moving warrants investigation.
In older pets, these signs are often attributed to “just aging” when they may actually indicate treatable conditions like osteoarthritis, hip dysplasia, intervertebral disc disease, or bone tumors.
8. Eye or Nasal Discharge
A small amount of clear discharge from the eyes or nose can be normal in some pets. However, thick, colored (yellow or green), or persistent discharge indicates infection, allergy, or other conditions requiring treatment.
Cloudiness or redness in the eyes, squinting, pawing at the eyes, or obvious changes in the appearance of the eye are always worth having checked promptly — eye conditions can deteriorate rapidly.
9. Skin and Coat Changes
A healthy pet’s coat should be smooth, shiny, and free of excessive shedding, bald patches, flakes, or unusual odor. Changes in coat quality can reflect nutritional deficiencies, hormonal imbalances, parasites, allergies, or systemic disease.
Excessive scratching, licking, or chewing at the skin — particularly in the same area repeatedly — indicates discomfort that may be caused by fleas, allergies, infection, or pain in that area.
10. Swelling or Lumps
Any new lump, bump, or area of swelling should be evaluated by a veterinarian. While many lumps in pets are benign (lipomas, cysts), others are malignant and early detection dramatically improves treatment outcomes.
Don’t assume a lump is harmless because it’s small or because your pet doesn’t seem bothered by it. Regular whole-body checks — running your hands over your pet’s entire body once a month — help you notice new lumps early.
11. Bad Breath, Drooling, or Difficulty Eating
Significant bad breath in pets is not normal — it usually indicates dental disease, which affects the majority of dogs and cats over three years old. Untreated dental disease causes pain, infection, and can contribute to kidney, liver, and heart disease through bacterial spread.
Excessive drooling, dropping food, chewing on one side, or reluctance to eat hard food can indicate dental pain, mouth injury, or nausea.
12. Behavioral Changes
Sudden changes in behavior — increased aggression, unusual fearfulness, hiding, clinginess, or a generally altered personality — are often the earliest signs that a pet is unwell or in pain. Animals in pain frequently become irritable or withdrawn.
If your normally social dog suddenly snaps when touched in a specific area, or your friendly cat starts hiding under the bed, take it seriously.
13. Distended or Painful Abdomen
A visibly swollen or hard abdomen combined with restlessness, unproductive retching, and distress is a potential emergency called bloat (gastric dilatation-volvulus or GDV) in large-breed dogs — a life-threatening condition requiring immediate surgery.
Any obvious abdominal pain or distension warrants prompt veterinary evaluation.
14. Neurological Signs
Seizures, loss of coordination, head tilting, circling, sudden blindness, or paralysis are all neurological emergencies. Even a single seizure in a pet that has never had one before warrants same-day veterinary evaluation.
15. Pale, White, Blue, or Yellow Gums
Your pet’s gums are one of the most useful health indicators available. Healthy gums should be pink and moist. Press them gently — they should briefly turn white and return to pink within 2 seconds (capillary refill time).
Pale or white gums indicate poor circulation or severe anemia. Blue or grey gums indicate oxygen deprivation. Yellow gums indicate jaundice. All of these are emergencies.
When to Call the Vet vs. When to Go to Emergency
Call your regular vet for: any symptom lasting more than 24–48 hours, new lumps, coat changes, mild limping, behavioral changes, and routine concerns.
Go to emergency immediately for: difficulty breathing, suspected poisoning, urinary blockage, seizures, pale or blue gums, suspected bloat, severe trauma, loss of consciousness, or any symptom that suddenly and severely worsens.
→ Read Next: How to Choose the Right Veterinarian for Your PetThe Bottom Line
You know your pet better than anyone. Trust your instincts — if something feels off, it probably is. Regular veterinary checkups, combined with attentive daily observation, are the foundation of keeping your animal healthy for as long as possible. When in doubt, call your vet. It’s always better to check and find nothing wrong than to wait and wish you’d acted sooner.
Emma Hartwell is a lifelong animal lover, certified pet nutritionist, and experienced dog trainer with over 8 years of hands-on experience working with animals of all kinds. She founded InnerzNews to give pet owners access to honest, practical, and science-backed advice — because every animal deserves the best possible care. When she’s not writing, Emma is hiking with her two rescue dogs, Milo and Biscuit, or volunteering at her local animal shelter.