If your dog is slowing down, your dog just sleeps all day, or they're refusing to play like they used to, chances are they're not simply being lazy. Lethargic dogs or pets who show signs of exercise intolerance may have a serious underlying condition. In particular, this may be caused by a serious condition like heart disease. If your dog's acting tired, your dog seems lethargic or is simply less active than usual, it's important to pay attention to these cues. Keep reading to understand why your dog may have exercise intolerance and what you should do about it.

Possible Causes of Lethargy

It's normal for some dogs to slow down a bit after heavy activity. For example, your dog may want to spend a day or two sleeping more than usual following a long day at the dog park or a rigorous hike. However, prolonged tiredness should not be ignored. Exercise intolerance is only one red flag for major issues like heart disease, but it could also signal a host of other problems, ranging from mild issues, such as muscle pain, to serious conditions like congestive heart failure. Vets Now lists several potential reasons why your dog has low energy:

  • Infection or illness
  • Heart problems
  • Liver problems
  • Diabetes or hypoglycemia
  • Hypothyroidism
  • Parasites
  • Side effects of medication
  • Poisoning or trauma

The walking service and dog advice site, Wag!, adds that exercise intolerance in combination with other symptoms—such as a lack of appetite, coughing, or fainting—could also be a sign of pulmonary hypertension (high blood pressure in the lungs) or other cardiovascular disease.

Signs of Exercise Intolerance and Lethargy in Dogs

It's usually fairly easy to tell if your dog's tired or acting sluggish, and you may wonder, "Why is my dog acting lethargic?" Excessive sleep, low energy, lack of excitement, and delayed responses are all overt signs of a lethargic dog, says Vetinfo. Exercise intolerance can be harder to spot, especially if you don't walk or play with your dog regularly. In milder cases, says Wag!, your pooch may simply not want to walk as far or play as much as normal. Coughing, heavy panting, or labored breathing following physical activity might also signal exercise intolerance. Extreme cases might involve confusion, disorientation, a lapse in toilet training, a rise in body temperature, wobbliness and even collapse.

What You Should Do to Help

If you notice that your dog is acting lethargic or isn't tolerating their usual levels of exercise, it's important not to force them to run. Follow their cues, and allow them to stop playing or cut the walk short if necessary. Keep a close eye on them, watching for other serious symptoms. If you notice any other worrisome behaviors, you should contact your veterinarian right away. If your tired dog doesn't show any other symptoms, wait a day or two. If your pup's energy doesn't improve or the condition worsens, contact your veterinarian. That being said, if they show extreme symptoms, such as fainting or collapsing, get them to an emergency clinic immediately.

Diagnosing Your Dog

Once at the veterinarian, your dog will be thoroughly examined. The veterinarian will likely look for any signs of lameness, injury, or pain, as well as any possible tumors. He or she will also perform blood and urine tests to check for underlying health conditions. It's likely that your dog will also be hooked up to an electrocardiograph machine to check the electrical activity of their heart, and will be given chest X-rays to examine their heart and lungs. Your veterinarian might also recommend an ultrasound, CT scan, or MRI to help diagnose your pup's condition. You can help achieve a proper diagnosis by providing your veterinarian with a list of any medications your dog takes, talking over the details about their diet and lifestyle, and mentioning any other symptoms or changes you've noticed in your pup.

What to Do After Diagnosis

Lethargy and exercise intolerance are symptoms of a problem, not a condition by themselves. The type of care your lethargic dog needs will depend on the condition with which they're diagnosed. Depending on the veterinarian's assessment, your pooch might recover and return to their former levels of activity. However, heart disease in dogs, as well as other progressive illnesses, may require changes in exercise and activity for the rest of your dog's life. Talk to your veterinarian about your pup's condition and follow their recommendation.

Jean Marie Bauhaus Jean Marie Bauhaus

Jean Marie Bauhaus is a pet parent, pet blogger, and novelist from Tulsa, Oklahoma, where she usually writes under the supervision of a lapful of fur babies.