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Common Pet Symptoms: When to Worry and When to See the Vet

Editorial note: This article is purely educational and does not replace professional veterinary diagnosis or treatment. We do not recommend, endorse, or rank any specific veterinary practice, medication, or treatment protocol. Our goal is to help you recognize common symptoms in dogs and cats, understand what they might mean, and know when your pet needs professional veterinary care. For our full editorial policy, see our Editorial Standards.

Every pet owner has experienced that moment of worry: your dog is limping, your cat stopped eating, or your pet just seems "off." Some symptoms resolve on their own, while others signal a serious medical condition that requires prompt attention. Knowing the difference can save your pet's life—and save you from unnecessary panic or delayed treatment.

This guide covers the ten most common symptoms pet owners encounter in dogs and cats. For each symptom, we explain the likely causes, what you can safely monitor at home, when to schedule a regular vet appointment, and when to seek emergency care immediately. Use this as a reference when something seems wrong with your pet, but always err on the side of caution: if you are unsure, calling your veterinarian is never the wrong decision.

1. Vomiting (Dogs and Cats)

Vomiting is one of the most common reasons pet owners seek veterinary advice. Both dogs and cats vomit occasionally, and a single isolated episode is usually not cause for alarm. However, frequent, persistent, or severe vomiting can indicate serious underlying conditions that require medical attention.

Common Causes

In dogs, the most frequent causes of vomiting include dietary indiscretion (eating something they should not have, such as garbage, table scraps, or non-food items), eating too fast, sudden diet changes, motion sickness, intestinal parasites, infections (viral or bacterial gastroenteritis), pancreatitis, foreign body obstruction, toxin ingestion, kidney disease, liver disease, and bloat (gastric dilatation-volvulus in large breeds). In cats, common causes include hairballs, eating too quickly, dietary sensitivity, intestinal parasites, inflammatory bowel disease (IBD), kidney disease (especially in senior cats), hyperthyroidism, foreign body ingestion (particularly string and hair ties), pancreatitis, and toxin exposure (lilies are extremely dangerous for cats).

When It Is Likely Not Serious

A single episode of vomiting followed by normal behavior, normal appetite, and no other symptoms is usually benign. Dogs that eat grass and then vomit, or cats that occasionally produce a hairball, are exhibiting normal behavior. If your pet vomits once, seems fine afterward, and resumes eating and drinking normally within a few hours, you can typically monitor at home.

Home Care

When to Call the Vet

When It Is an Emergency

2. Diarrhea

Diarrhea—loose, watery, or abnormally frequent stools—is extremely common in both dogs and cats. Like vomiting, it can range from a minor and self-limiting digestive upset to a symptom of a serious or life-threatening condition. The duration, severity, and accompanying symptoms are what determine how urgently your pet needs veterinary care.

Common Causes

Dietary indiscretion or sudden food changes, stress (boarding, travel, new environment), intestinal parasites (roundworms, hookworms, giardia, coccidia), viral infections (parvovirus in dogs, panleukopenia in cats), bacterial infections (salmonella, campylobacter), food allergies or sensitivities, inflammatory bowel disease, pancreatitis, and medications (especially antibiotics) are all common triggers. In puppies and kittens, parasites and viral infections are particularly common and can become serious quickly due to their small body size and limited reserves.

Why Duration Matters

Acute diarrhea (lasting 1 to 2 days) is often self-limiting and resolves with basic supportive care. Diarrhea lasting more than 48 hours warrants veterinary attention because prolonged fluid loss leads to dehydration, electrolyte imbalances, and weakness, particularly in small, young, or elderly pets. Chronic diarrhea (lasting weeks to months, even if intermittent) indicates an underlying condition that needs diagnosis and treatment.

Dehydration Signs to Watch For

Dehydration is the primary danger of persistent diarrhea. Check for these signs:

Home Care

When to Call the Vet

When It Is an Emergency

3. Not Eating / Loss of Appetite

A pet that suddenly stops eating is one of the most common concerns that brings owners to the vet. Loss of appetite (medically called anorexia or inappetence) can be caused by something as minor as a picky eating day or as serious as organ failure. The timeframe for concern differs between dogs and cats, and understanding this distinction is critically important.

Common Causes

Stress or environmental changes, dental pain or oral disease, gastrointestinal upset (nausea, stomach pain), infections, pain from any source (musculoskeletal, abdominal, dental), kidney disease, liver disease, pancreatitis, cancer, medication side effects, and fever. In cats specifically, upper respiratory infections (which impair the sense of smell) are a very common cause of appetite loss because cats rely heavily on smell to determine whether food is appealing.

Dogs vs. Cats: Why the Timeframe Matters

Dogs can generally tolerate 24 to 48 hours without eating with minimal medical concern, as long as they are still drinking water and not showing other signs of illness. Some dogs simply skip a meal occasionally. Cats are different and more vulnerable. When a cat stops eating—particularly an overweight cat—the body begins mobilizing fat stores to the liver for energy processing. The feline liver is not designed to handle this rapid influx of fat, and within as little as 2 to 3 days, a dangerous condition called hepatic lipidosis (fatty liver disease) can develop. Hepatic lipidosis is life-threatening and requires aggressive veterinary treatment including hospitalization and assisted feeding, often through a feeding tube. This is why a cat not eating for more than 24 to 48 hours should always be taken seriously.

Home Care

When to Call the Vet

When It Is an Emergency

4. Limping / Lameness

Limping is one of the most visible signs that something is wrong with your pet, and "why is my dog limping?" is one of the most commonly searched pet health questions. The key distinction is whether the limping came on suddenly (acute) or has developed gradually over time (chronic), as this significantly narrows the list of possible causes and determines how urgently your pet needs to be seen.

Common Causes

Sudden onset (acute) limping: Paw pad injury (cut, thorn, burn from hot pavement), muscle strain or sprain, torn toenail, insect sting or bite, fracture, ligament tear (such as cranial cruciate ligament/CCL in dogs), joint dislocation, or trauma. Gradual onset (chronic) limping: Osteoarthritis (extremely common in older dogs and cats), hip dysplasia, elbow dysplasia, Lyme disease, bone tumors (osteosarcoma, particularly in large breed dogs), degenerative joint disease, or intervertebral disc disease (IVDD, common in breeds like Dachshunds, Corgis, and French Bulldogs).

Home Care

When to Call the Vet

When It Is an Emergency

5. Excessive Drinking and Urination

If your dog or cat is suddenly drinking much more water than usual (polydipsia) and urinating more frequently or in larger volumes (polyuria), this is a symptom that should always be evaluated by a veterinarian. While there can be benign explanations, increased thirst and urination are hallmark signs of several serious medical conditions that are most treatable when caught early.

Common Causes

In dogs: Diabetes mellitus, Cushing's disease (hyperadrenocorticism), kidney disease, urinary tract infection, liver disease, pyometra (uterine infection in unspayed females), hypercalcemia, and certain medications (steroids, diuretics). In cats: Chronic kidney disease (very common in older cats), diabetes mellitus, hyperthyroidism, urinary tract infection, and liver disease. Hot weather, increased exercise, and a recent switch from wet food to dry food can also increase water intake, but these are usually proportional and not dramatic.

What to Watch For

Home Care

When to Call the Vet

When It Is an Emergency

6. Coughing and Sneezing

Respiratory symptoms in pets range from an occasional harmless sneeze to signs of serious respiratory illness. The pattern, frequency, duration, and associated symptoms help determine whether your pet's coughing or sneezing is a minor annoyance or a medical concern.

Common Causes

Coughing in dogs: Kennel cough (infectious tracheobronchitis—a harsh, honking cough that sounds like a goose), heart disease (especially in small breeds and older dogs), collapsing trachea (common in small breeds like Yorkies, Pomeranians, and Chihuahuas), pneumonia, canine influenza, allergies, and inhaled foreign bodies. Coughing in cats: Feline asthma (the most common cause of chronic coughing in cats), upper respiratory infection, heart disease, pneumonia, lungworms, and inhaled irritants. Sneezing in both species: Upper respiratory infections (especially common in cats), allergies, nasal foreign bodies (grass awns are a common culprit), dental disease with root involvement reaching the nasal cavity, and nasal tumors (typically in older pets with chronic, progressive sneezing, often with nasal discharge from one side).

Home Care

When to Call the Vet

When It Is an Emergency

7. Lethargy / Low Energy

Lethargy—a noticeable decrease in energy, activity, and interest in the environment—is one of the most common but also most nonspecific symptoms in pets. Because lethargy accompanies such a wide range of conditions, from mild viral infections to cancer, it is best understood as your pet's way of telling you that something is wrong without specifying what. The challenge for pet owners is distinguishing between a pet that is simply having a lazy day and one that is genuinely ill.

Common Causes

Infections (viral, bacterial, tick-borne diseases like Lyme disease or ehrlichiosis), pain (from any source—dental, musculoskeletal, abdominal), fever, anemia, heart disease, respiratory disease, metabolic conditions (hypothyroidism in dogs, kidney disease, liver disease, diabetes), cancer, medication side effects, depression or grief, heat exhaustion, and post-vaccination lethargy (mild and short-lived, typically resolving within 24 to 48 hours).

How to Tell Normal Tiredness from Concerning Lethargy

Normal: Your pet sleeps more after a long hike, vigorous play session, or on a very hot day but returns to normal energy within a few hours. Your pet is less active but still responds normally to food, treats, your voice, and the doorbell. Concerning: Your pet does not want to get up for meals, walks, or activities they normally enjoy. They seem unresponsive or slow to react. They hide (especially cats). They do not greet you at the door when they normally would. The behavior change persists for more than a day or worsens progressively.

Home Care

When to Call the Vet

When It Is an Emergency

8. Itching and Scratching

Persistent itching (pruritus) that leads to scratching, licking, biting, or rubbing is extremely common in both dogs and cats. While the occasional scratch is normal, frequent or intense itching indicates an underlying issue that is causing discomfort. The two most common broad categories are allergies and parasites, though other conditions can also cause itching.

Common Causes

Parasites: Fleas (by far the most common cause of itching in pets; some pets have flea allergy dermatitis, where a single flea bite causes intense, widespread itching), mites (sarcoptic mange in dogs, ear mites in cats), and ticks. Allergies: Environmental allergies/atopy (pollen, dust mites, mold—often seasonal), food allergies (typically to a protein source like chicken, beef, or fish; develops over time with repeated exposure), and contact allergies (less common; reaction to something the skin touches). Other causes: Bacterial skin infections (pyoderma), yeast infections (particularly in skin folds, ears, and between toes), dry skin, ringworm (a fungal infection, not a parasite), and anxiety-related overgrooming (especially in cats).

Allergies vs. Parasites: Key Differences

Home Care

When to Call the Vet

When It Is an Emergency

9. Eye Discharge and Redness

Eye problems in pets should always be taken seriously because eye conditions can worsen rapidly and some can lead to permanent vision loss if not treated promptly. A small amount of clear discharge in the morning is normal, but persistent discharge, color changes, redness, squinting, or cloudiness are signs that something is wrong.

Common Causes

In dogs: Conjunctivitis (pink eye), allergies, corneal ulcers or scratches, dry eye (keratoconjunctivitis sicca/KCS), entropion (eyelids rolling inward), foreign bodies (grass seeds, dust), glaucoma, and breed-related issues (brachycephalic breeds like Bulldogs, Pugs, and Shih Tzus are more prone to eye problems due to their prominent eyes). In cats: Upper respiratory infections (herpesvirus and calicivirus commonly cause eye discharge in cats), conjunctivitis, corneal ulcers, feline herpesvirus flare-ups (recurrent throughout life), uveitis (inflammation inside the eye, which can be associated with systemic diseases like FIV, FeLV, or toxoplasmosis), and glaucoma.

What the Discharge Tells You

Home Care

When to Call the Vet

When It Is an Emergency

10. Ear Scratching and Head Shaking

When a dog or cat persistently scratches at an ear, shakes their head, or tilts their head to one side, it almost always indicates ear discomfort. Ear problems are among the top reasons for veterinary visits, particularly in dogs. While rarely life-threatening, untreated ear conditions cause significant pain and discomfort, and chronic ear problems can lead to permanent damage including hearing loss.

Common Causes

In dogs: Ear infections (otitis externa—very common, especially in breeds with floppy ears like Cocker Spaniels, Basset Hounds, Labradors, and Golden Retrievers), allergies (ear infections are one of the most common manifestations of environmental and food allergies in dogs), ear mites (more common in puppies), foreign bodies (grass awns/foxtails that enter the ear canal), and yeast overgrowth. In cats: Ear mites (the most common cause of ear problems in cats, especially kittens), ear infections (bacterial or yeast), polyps (benign growths in the ear canal or middle ear), and allergies. Signs of ear problems include scratching at the ears, head shaking, head tilting, redness or swelling of the ear flap or canal, discharge (brown, yellow, or black), a foul odor from the ears, pain when the ear area is touched, and loss of balance or walking in circles (if the middle or inner ear is affected).

Home Care

When to Call the Vet

When It Is an Emergency

Emergency Symptom Checklist: Red Flags Requiring Immediate Vet Care

Regardless of the specific symptom your pet is showing, the following signs should always prompt immediate emergency veterinary care. Print this list or save it on your phone for quick reference. When in doubt, call your nearest emergency veterinary hospital—they can provide phone triage to help you decide.

Try Our AI Symptom Checker

For additional guidance on your pet's symptoms, try our AI-Powered Pet Symptom Checker. This free tool lets you describe your pet's symptoms and receives personalized guidance on possible causes, home care recommendations, and whether veterinary attention is recommended. It is available 24/7 and covers dogs, cats, birds, reptiles, fish, and small animals.

Please remember: the symptom checker provides general educational guidance and is not a substitute for professional veterinary diagnosis. If your pet is showing emergency symptoms listed above, skip the symptom checker and go directly to an emergency veterinary hospital.

Frequently Asked Questions

When should I take my dog or cat to the vet for vomiting?

A single episode of vomiting in an otherwise healthy, alert pet is usually not an emergency. However, you should see the vet promptly if your pet vomits more than two or three times in a day, vomits blood or material that looks like coffee grounds, cannot keep water down for more than 12 hours, appears lethargic or in pain, has a bloated or distended abdomen, or if vomiting is accompanied by diarrhea, fever, or loss of appetite lasting more than 24 hours. Puppies, kittens, senior pets, and pets with existing health conditions should be seen sooner, as they have less physiologic reserve.

Why is my dog limping and when should I worry?

Dogs limp for many reasons, from minor muscle strains and thorn pricks to serious conditions like fractures, ligament tears, or joint disease. Sudden limping after activity is often a soft tissue injury that may improve with 24 to 48 hours of rest. However, seek veterinary care immediately if your dog cannot bear any weight on the leg, the limb appears deformed or is at an abnormal angle, there is significant swelling, your dog is in obvious pain (crying, panting, refusing to move), or if there was known trauma. Limping that persists beyond 48 hours, worsens over time, or recurs frequently should always be evaluated by a veterinarian.

How long can a cat go without eating before I should worry?

Cats should not go without eating for more than 24 to 48 hours. Unlike dogs, cats are uniquely susceptible to a serious liver condition called hepatic lipidosis (fatty liver disease) when they stop eating, which can develop in as little as 2 to 3 days of not eating, especially in overweight cats. If your cat has not eaten anything in 24 hours and shows other signs of illness (lethargy, hiding, vomiting), contact your vet that day. If your cat refuses food for 48 hours even without other symptoms, a veterinary visit is necessary.

What are the emergency symptoms in pets that require immediate veterinary care?

Seek emergency veterinary care immediately if your pet shows difficulty breathing or choking, uncontrolled bleeding, pale or blue gums, collapse or inability to stand, seizures lasting more than three minutes, suspected poisoning, bloated or hard abdomen with unproductive retching, inability to urinate (especially male cats), sudden paralysis of the hind legs, loss of consciousness, severe trauma, extreme pain, or body temperature above 104°F or below 99°F. When in doubt, call your nearest emergency vet hospital for phone triage.

Can I treat my pet's symptoms at home or do I always need a vet?

Some mild symptoms can be monitored at home for a short period. A single episode of vomiting or soft stool, mild sneezing, minor limping that improves with rest, or brief appetite loss in an otherwise alert and active pet may resolve on its own within 24 to 48 hours. However, you should never give human medications to pets without veterinary guidance, as many common medications like ibuprofen and acetaminophen are toxic to dogs and cats. If symptoms persist beyond 48 hours, worsen, or are accompanied by lethargy, fever, pain, or refusal to eat or drink, always consult a veterinarian. Puppies, kittens, senior pets, and pets with chronic conditions have less reserve and should be seen sooner.

Related Resources

For more information on managing your pet's health, explore these related guides on our site:

Disclaimer: This article is for educational purposes only and does not constitute veterinary medical advice, diagnosis, or treatment. The symptom information provided is general guidance and cannot account for your individual pet's health history, breed-specific risks, or current medications. Always consult a licensed veterinarian for medical concerns about your pet. Do not delay seeking professional veterinary care based on information in this guide. If you believe your pet is experiencing a medical emergency, contact your nearest emergency veterinary hospital immediately. See our Medical Disclaimer for complete details.

Last updated: March 2026 · Editorial Standards