Dog Weakness and Lethargy: Causes and Treatments


In this Article

  • When to See a Vet
  • Dog Weakness and Lethargy: Common Causes and Treatments
  • Other Causes of Weakness and Lethargy in Dogs

Lethargy and weakness — these are vague but common symptoms of illness in dogs. And many things, some of them quite serious, can make your dog weak or lethargic. Here’s information about the most common conditions, how they are treated, and when your dog should see a vet.

When to See a Vet

Things that can make your dog lethargic and weak can range from infection and disease to pain and medication. And because weakness and lethargy can indicate anything from a chronic condition to a life-threatening illness, you should always talk to your vetwhen you notice either symptom.

Dog Weakness and Lethargy: Common Causes and Treatments

A few of the more common causes of weakness or lethargy in dogs include the following:

Infection. Any kind of infection — including serious ones such as parvovirus, distemper, kennel cough, leptospirosis, and heartworm disease — can make your dog lethargic.

  • Parvovirus is spread through feces. Symptoms of parvo can include lethargy, vomiting, diarrhea, and abdominal pain. Treatment includes aggressive supportive care with fluids, anti-nausea medications, and antibiotics.
  • Distemper can cause symptoms such as fever, lethargy, discharge from the eyes and nose, and coughing. It may cause neurological problems. The signs of distemper are broad and vary from dog to dog. Treatment may include antibiotics, fluids, and anticonvulsants.
  • Kennel cough is a contagious respiratory disease. Its most distinctive symptom is a dry, honking cough. Dogs with kennel cough can be lethargic and feverish. Treatments may include cough suppressants, antibiotics, and bronchodilators.
  • Heartworm disease is caused by heartworms that are transmitted through mosquito bites. Symptoms of heartworm infection can include lethargy, depression, fever, and weakness. Prevention with oral or injectable medicines is the best option. Treatment for existing disease requires a series of injections and medications and months of strict cage rest.

Metabolic and Organic Disease. A wide range of chronic conditions can leave dogs weak or lethargic. That includes heart problems, liver problems, diabetes, and hypoglycemia.

  • Heart disease. Lethargy and reduced tolerance for exercise are the early signs of congestive heart failure in dogs. As the condition worsens, other symptoms develop, including loss of appetite, coughing, and rapid breathing. Treatment depends on how far along the condition is. It may include heart medication, diuretics, and diet changes.
  • Liver disease. Signs of liver disease in dogs include lethargy, loss of appetite, jaundice (yellow tint to gums or whites of eyes), depression, and abdominal bloating. Treatment of liver disease is critical and may include medication, diet changes, or surgery.
  • Diabetes mellitus. Signs your dog may have diabetes include lethargy, excessive thirst and urination, weight loss, and changes in appetite. Treating diabetes requires insulin injections, along with diet adjustments.
  • Hypoglycemia. This is low blood sugar, which is the opposite of diabetes. It can make your dog weak and lead to seizures. Treatment will depend on what’s causing the hypoglycemia. Short-term therapy may include giving corn syrup orally or intravenous glucose.

Medications. A broad range of medications for dogs can make your pet lethargic or weak. If you notice weakness after starting a new drug or using a new flea or heartworm product, call your veterinarian immediately.

Many human medications, such as ibuprofen, are toxic to pets. They can lead to weakness, lethargy, even death. So always keep human drugs out of reach of your pet. If you drop a pill, pick it up immediately — before your dog does. Also, be sure any drugs you discard in the trash can’t be reached by your pooch.

If you think your dog has consumed human medication — or anything that might be toxic — call your vet at once or call the Animal Poison Control Center at (888) 426-4435.

Other Causes of Weakness and Lethargy in Dogs

Any of the following can cause weakness and lethargy in dogs:

  • Tumors/cancer
  • Pain
  • Trauma
  • Chronic or acute diarrhea
  • Snake bite
  • Hypothyroidism and other hormone problems
  • Anemia
  • Poisoning (for example from eating foods that are toxic to dogs, like garlic, leeks, or onions)
  • Anal gland problems

Because so many things can cause weakness or lethargy in your dog, always give your vet a call if you notice these symptoms.

Show Sources


Fogle, B. Caring for Your Dog, Dorling Kindersley, Ltd., 2002.

National Institutes of Health, Veterinary Medicine Labels: “Clomicalm (clomipramine hydrochloride) Tablet, Clomipramine (clomipramine hydrochloride) Powder.”

American College of Veterinary Internal Medicine: “Chemotherapy.”

Camrose Animal Clinic: “Diethylstilbestrol.”

Desert Labrador Retriever Rescue: “What’s Valley Fever.”

Canine Liver Disease Foundation: “Treatment Options for Canine Liver Disease” and “Signs and Symptoms of Canine Liver Disease.”

Department of Agriculture and Food: “Health Care of the Farm Dog.”

ASPCA: “Animal Poison Control Center.”

Humane Society of Utah: “Year Round Heartworm Testing & Medication Provides the Protection Your Pet Needs.”

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