1. Loss of appetite, weight loss. Often, loss of appetite is the very first sign of an underlying illness in pets. There can be many reasons your dog isnít hungry or refuses to eat, but not eating can begin to negatively impact his health within 24 hours. And for puppies 6 months or younger, the issue is even more serious.Weight loss is the result of a negative caloric balance, and it can be the consequence of anorexia (loss of appetite) or when a dogís body uses or eliminates essential dietary nutrients faster than they are replenished. Weight loss exceeding 10 percent of your dogís normal body weight will be a red flag for your vet. There can be several underlying causes, some of which are very serious.
  2. Lethargy, extreme fatigue. A lethargic dog will appear drowsy, ďlazy,Ē and/or indifferent. She may be slow to respond to sights, sounds and other stimuli in her environment.Lethargy or exhaustion is a non-specific symptom that can signal a number of potential underlying disorders, including some that are serious or life-threatening. If your pet is lethargic for longer than 24 hours, itís time to make an appointment with your veterinarian.
  3. Coughing. Coughing in dogs, unless itís a one-and-done situation, generally indicates an underlying problem. Examples include a possible windpipe obstruction, kennel cough, bronchitis, pneumonia, heartworm disease, heart failure, and tumors of the lung.All causes of coughing require investigation, and in most cases, treatment.
  4. Fever. If your dogís temperature spikes, it usually means his body is fighting an infection. The normal temperature in dogs is 100.5 to 102.5 degrees F. If your pet feels warm to you and his temp is higher than normal, make an appointment with your veterinarian.
  5. Difficulty breathing. A dog in respiratory distress will have labored breathing or shortness of breath that can occur when she breathes in or out. Breathing difficulties can mean that not enough oxygen is reaching her tissues. Additionally, dogs with heart failure may not be able to pump enough blood to their muscles and other tissues.Respiratory distress often goes hand-in-hand with a buildup of fluid in the lungs or chest cavity that leads to shortness of breath and coughing. If your dog has sudden undiagnosed breathing problems, she should see a veterinarian immediately.
  6. Trouble urinating. This includes discomfort while urinating, straining to urinate, and frequent attempts to urinate with little success. If your dog cries out while relieving himself, seems preoccupied with that area of his body or is excessively licking the area, you should make an appointment with your veterinarian right away.There are several underlying causes of urinary difficulties, some of which can result in death within just a few days.
  7. Bloody diarrhea, urine, vomit. Digested blood in your dogís poop will appear as black tarry stools. Fresh blood in the stool indicates bleeding in the colon or rectum. Either situation is cause for concern and should be investigated as soon as possible.Blood in a dogís urine, called hematuria, can be obvious or microscopic. There are a number of serious disorders that can cause bloody urine, including a blockage in the urinary tract, a bacterial infection, and even cancer.
    Vomited blood can be either bright red (fresh), or resemble coffee grounds (indicating partially digested blood). There are a variety of reasons your dog might vomit blood, some of which are relatively minor, but others are serious and even life threatening.
  8. Pacing, restlessness, unproductive retching. When a dog paces and seems unable or unwilling to settle down, it can signal that heís in pain, discomfort, or distress. One very serious condition in which these symptoms are common is gastric dilatation volvulus (GDV), also called bloat. Another sign of bloat is when a dog tries to vomit but brings nothing up.Bloat is a life-threatening condition that most often occurs in large breed dogs and those with deep chests.
  9. Fainting, collapsing. When a dog collapses, it means she experiences a sudden loss of strength that causes her to fall and not be able to get back up. If a collapsed dog also loses consciousness, she has fainted.Either of these situations is an emergency, even if your dog recovers quickly and seems normal again within seconds or minutes of the collapse. All the reasons for fainting or collapsing are serious and require an immediate visit to your veterinarian. They include a potential problem with the nervous system (brain, spinal cord or nerves), the musculoskeletal system (bones, joints, muscles), the circulatory system (heart, blood vessels, blood), or the respiratory system (mouth, nose, throat, lungs).
  10. Red eye(s). If the white area of your dogís eye turns bright red, itís a sign of inflammation or infection that signals one of several diseases involving the external eyelids, the third eyelid, the conjunctiva, cornea, or sclera of the eye.Redness can also point to inflammation of structures inside the eye, eye socket disorders, and also glaucoma. Certain disorders of the eye can lead to blindness, so any significant change in the appearance of your dogís eyes should be investigated.

Some symptoms of illness in dogs are best handled by simply giving them a chance to run their course, for example, a temporary GI upset resulting from indiscriminate snacking.


Other symptoms can be so sudden, severe and frightening that you know immediately you need to get your pet to the vet or an emergency animal hospital.