Top 10 Signs Your Dog Might Be Sick

1. Loss of Appetite or Unusual Eating Habits

Food is typically one of a dog’s greatest joys. A healthy dog will usually have a consistent appetite, so when your pup suddenly refuses to eat or drastically changes their eating patterns, it’s often a sign of a deeper issue. It could indicate dental problems, nausea, an obstruction in the digestive tract, or systemic illnesses like kidney disease, liver failure, or cancer.

Be alert to not only whether your dog eats but how they eat. Do they approach the food bowl and walk away? Are they chewing slower than usual? Do they seem interested in food but unable to eat? A complete loss of appetite that lasts longer than 24 hours, especially when paired with lethargy or vomiting, warrants an immediate trip to the vet. Also watch for weight loss despite normal eating, which may indicate metabolic disorders or malabsorption conditions.

2. Lethargy or Reduced Activity Levels

Most dogs—regardless of age—have a predictable pattern of activity. Even older dogs will usually perk up for walks, food, or favorite toys. If your normally active dog suddenly becomes disinterested in movement or seems tired after minimal exertion, pay attention.

Lethargy can be caused by everything from minor infections to major systemic diseases, including anemia, heart disease, or endocrine disorders like hypothyroidism. It’s not just about sleepiness—lethargy is a state where the dog seems mentally and physically slower, less responsive to stimuli, and detached from the environment. If this persists for more than a day or is accompanied by other symptoms like shivering, vomiting, or labored breathing, consult your vet without delay.

3. Vomiting, Diarrhea, or Digestive Upset

Digestive disturbances are among the most common signs that something’s wrong with your dog. Occasional vomiting or a loose stool might not be alarming, especially if your dog is otherwise alert and eating normally. But frequent episodes or the presence of blood, mucus, or black, tarry stools are much more serious.

Gastrointestinal distress can result from a wide range of causes, including food intolerance, infections, parasites, ingestion of toxins or foreign objects, or chronic illnesses like inflammatory bowel disease. Persistent vomiting or diarrhea leads quickly to dehydration, which can be dangerous—especially for puppies, elderly dogs, or small breeds. Keep an eye on frequency, color, and consistency, and always bring a stool sample when visiting your vet.

4. Labored Breathing, Wheezing, or Constant Coughing

Dogs should breathe easily and quietly at rest. Heavy panting after exercise is normal, but labored breathing during relaxation or sleep is not. If your dog shows signs of respiratory distress—such as wheezing, shallow breaths, or flaring nostrils—it could indicate conditions like kennel cough, pneumonia, asthma, or congestive heart failure.

Coughing is another symptom that varies in significance. A dry, hacking cough might indicate tracheal collapse (common in toy breeds), while a wet, productive cough could signal bronchitis or pneumonia. Dogs suffering from heartworm disease often have a chronic cough as one of the first warning signs. If your dog’s breathing is noisy, their gums are turning pale or blue, or they’re coughing persistently for more than a day or two, seek emergency care.

5. Excessive Thirst and Urination

Drinking a little more water during hot weather or after exercise is expected. But if your dog suddenly starts emptying their water bowl more than usual or needing to go outside frequently—even during the night—it’s a potential red flag. Increased thirst (polydipsia) and urination (polyuria) are commonly associated with diabetes, kidney failure, urinary tract infections, and Cushing’s disease.

Incontinence or accidents in a house-trained dog are another clue something is wrong. Some dogs with bladder infections or stones may strain to urinate or whimper during the process. Keep an eye on how often your dog drinks and pees, and monitor for unusual odors, blood, or cloudiness in their urine. Early intervention can help prevent kidney damage and other complications.

6. Sudden Behavior or Mood Changes

One of the most subtle yet telling signs your dog might be ill is a sudden shift in behavior or temperament. If your usually affectionate pup becomes withdrawn, irritable, or aggressive, they may be in pain or discomfort. Likewise, a shy or quiet dog who becomes hyperactive or anxious could also be experiencing neurological symptoms or hormonal imbalances.

Behavioral changes can stem from many sources—pain, disorientation, fever, gastrointestinal upset, or even cognitive dysfunction in senior dogs. Pay close attention if your dog starts hiding, growling more, seeking isolation, or pacing obsessively. Dogs may also exhibit repetitive behaviors like licking their paws or biting their tail excessively. These signs often emerge before more physical symptoms show up, making them crucial to recognize early.

7. Changes in Skin, Coat, or Odor

Healthy dogs have clean, soft coats and neutral odors. If your dog starts to develop greasy fur, bald patches, or persistent scratching, it may signal underlying problems such as skin infections, mange, flea infestations, or food allergies. A coat that loses its shine or feels brittle and dry can also reflect internal illnesses like thyroid dysfunction or malnutrition.

Odors are another important clue. A strong, yeasty smell might indicate a fungal infection, while musty or rancid odors can suggest bacterial overgrowth. Don’t ignore foul smells coming from your dog’s ears, mouth, or skin folds—these often signal localized infections that can worsen quickly if untreated. Keep an eye out for rashes, lumps, or wounds that don’t heal. Many skin conditions are easier to treat when caught early and before they become chronic.

8. Noticeable Weight Gain or Loss

Weight fluctuation in dogs—either up or down—can be an early sign of illness. Sudden weight loss without changes in diet or activity may point to diabetes, hyperthyroidism, cancer, or digestive disorders that prevent proper absorption of nutrients. You might notice your dog’s ribs or hip bones becoming more prominent, or that their overall appearance seems gaunt despite a normal appetite.

On the other end, rapid weight gain can signal problems like Cushing’s disease, hypothyroidism, or fluid retention due to heart or liver issues. You may notice bloating in the abdomen or puffiness in the legs. Obesity itself is also a health risk that can lead to arthritis, heart disease, and diabetes. Monitoring your dog’s body condition regularly can help you catch health shifts before they become emergencies.

9. Mobility Issues or Trouble Moving

Changes in the way your dog walks or moves can indicate pain or injury. Limping, favoring one leg, or stiffness—especially after waking—may be signs of arthritis, joint dysplasia, or ligament damage. Dogs who previously loved jumping or climbing stairs may become hesitant or fearful, a possible indication of hip, spine, or neurological issues.

Some mobility issues are more subtle. Watch for signs like hesitation during walks, trembling while standing, or dragging the hind legs. Neurological conditions like intervertebral disc disease (IVDD) or degenerative myelopathy may cause loss of coordination or muscle atrophy. If your dog seems suddenly unbalanced, unsteady, or disoriented, don’t wait—get a diagnosis quickly to prevent irreversible damage.

10. Eye or Nose Discharge and Facial Changes

The eyes and nose are windows to your dog’s overall health. Clear eyes with minimal tearing and a moist nose are normal. But thick, greenish, or yellow discharge from the eyes or nose may indicate bacterial or viral infections. Red, swollen eyes, excessive blinking, or squinting could suggest conjunctivitis, glaucoma, or even corneal ulcers.

Nasal discharge paired with sneezing and coughing may point to respiratory infections or allergies, while bloody or unilateral discharge from one nostril can sometimes indicate polyps or tumors. Changes in your dog’s facial structure—like puffiness around the eyes or jaw, drooping eyelids, or asymmetry—might be signs of dental abscesses, trauma, or nerve damage. Always investigate these symptoms promptly, as the eyes, nose, and sinuses are vulnerable areas that can deteriorate rapidly if ignored.

Be Your Dog’s Health Advocate

Your dog depends on you to be their voice when they can’t explain what’s wrong. Recognizing the early signs of illness gives you the power to act fast and prevent pain, discomfort, or serious long-term complications. Dogs may not complain, but their behavior, appetite, mobility, and appearance will tell you everything—if you know what to look for.

Keep a written log of any changes you observe, even minor ones, and share this with your veterinarian during checkups. Maintain regular wellness visits, especially for senior dogs, and don’t hesitate to ask questions or get a second opinion. With proper awareness, quick responses, and compassionate care, you can ensure your dog enjoys a healthy, happy life by your side for years to come.