Dog Weakness and Lethargy: Causes and Treatments

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 vet when 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. 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 find their way into your dog through mosquito bites. Symptoms of heartworm infection can include lethargy, depression, fever, and weakness. Prevention is the best option. That includes keeping pets indoors at dusk (when mosquitoes feed) and giving them monthly preventive medicines. Treatment for existing disease requires a series of injections and weeks of strict cage rest.

Metabolic and Organic Disease.

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 and rapid breathing. Treatment depends on how far along the condition is. It may include ACE inhibitors, diuretics, and diet changes.
Liver disease. Signs of liver disease in dogs include lethargy, loss of appetite, jaundice, 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, 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
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)