Why Is My Dog Lethargic?

Stephanie Lantry, DVM
By Stephanie Lantry, DVM on Oct. 29, 2021

Lethargy is a symptom that can show up with many different health issues in dogs. If your dog is acting lethargic, the only way to truly determine the cause and the best treatment is having a veterinarian examine them.

Here’s what you need to know about lethargic dogs, from how to tell lethargy apart from tiredness, possible causes of lethargy in dogs, and when to call the vet.

What Is Lethargy in Dogs?

Lethargy is defined as a lack of energy and enthusiasm, but what does that mean for your dog? It is an important distinction to know if your dog is truly lethargic (which could indicate a medical issue) or is just tired.

It may be difficult to make that distinction, but you know your dog better than anyone. Recognizing when your dog is lethargic and being proactive helps your veterinarian give your dog the best care.

What’s the Difference Between a Lethargic Dog and a Tired Dog?

A dog that is lethargic is unusually inactive and not interested in getting up and doing normal activities. The severity of lethargy can vary but ranges from just moving more slowly to really having no interest in walks or play.

A tired dog may just be sleeping but is easily roused and ready to pop up if they hear the treat jar or the jingle of the leash.

Is It Normal for a Dog to Be Lethargic?

If you have a good explanation for your dog to be tired, then that may be the case.

If you have taken a very long walk or had a large amount of exercise (especially in the heat), then your dog may sleep for hours afterward. If your dog has been at day care or a boarding kennel, they may be really excited and on alert most of the time there and then come home and just crash.

If there is no unusual activity or exertion that would cause your pet to sleep more or be acting more tired than usual, then you may be dealing with lethargy and your dog may need veterinary attention.

Just like humans, dogs need more sleep when they are very young or very old. Young puppies are like babies and spend most of their time eating and sleeping. However, puppies are also relatively easy to rouse, and a difficult-to-wake puppy may mean something else is going on. For example, if you have difficulty waking your puppy, you may be dealing with a case of low blood sugar.

Senior dogs also need more time napping and get tired more easily after walks and playing. They also may not hear as well, so they might not wake up as easily when you come in. Once they are roused, though, they should be awake and ready to engage if they are truly just tired and not lethargic.

What Causes a Dog to Be Lethargic?

Causes of lethargy in dogs can vary by age. Here are some of the most probable causes of lethargy in dogs at each life stage.

Lethargy in Dogs of All Ages

Dogs of any age can become lethargic with any sickness, such as an infection or injury. Low thyroid levels can cause of lethargy in dogs; this is especially common in Golden Retrievers, Labrador Retrievers, Dobermans, Dachshunds, and Boxers.

Recognizing that your dog is lethargic early on and getting your dog treated by the vet before their symptoms get worse can really make a difference. This can help your dog get back to normal as soon as possible.

Lethargy in Puppies

Young puppies can suffer from hypoglycemia (low blood sugar), which can cause profound lethargy. This is most common in pups less than 4 months of age and in toy breeds. Their livers do not have the reserves to increase blood sugar, especially if they aren’t eating well.

Sometimes they don’t eat well if they are adjusting to their new home or if they have eaten something that they shouldn’t, which throws off their normal appetite.

Lethargy in Senior Dogs

Senior dogs are more often affected by arthritis and other joint conditions that cause pain. Dogs tend to hide their pain until they can’t take it any longer, so if your dog is not eager to get up and do the things they normally do, you should really pay attention to this and get them some help.

Seniors are also more prone to having internal problems with their organs, such as tumors or heart problems. This causes a real lack of energy that may be the first symptom you see.

When Should You Call a Vet About Lethargy in Your Dog?

If you are concerned that your dog is truly lethargic and not acting like they usually do, it is never the wrong thing to call your vet to get them checked out sooner rather than later.

Take your dog to the veterinarian immediately if they are lethargic and have any of the following symptoms, which are signs of an emergency:

  • Pale gum color (can indicate internal bleeding and can lead to life-threatening anemia)
  • Distended abdomen (can be a sign of bloat or other abdominal emergencies)
  • Labored breathing or blue or purple tongue color (often due to heart or lung problems that need urgent medical attention)

Lethargic Dogs With Other Symptoms

If your dog is lethargic, they may also have other symptoms. Here are some common symptoms you might see alongside lethargy and what these combinations mean.

Lethargic and Shaking

If your dog is lethargic and shaking, it is most commonly a sign of pain. You may not know where the pain is, but it’s a sign that your dog is in distress and is not feeling well. Sometimes the dog isn’t sure what is going on either and is trying to move as little as possible so they don’t hurt as much.

It could be spinal pain caused by an inflamed disc or another neurologic issue. Soft tissue injury or gastrointestinal pain often cause lethargy and shaking as well. These symptoms can also be signs of a fever.

Lethargic and Not Eating

This is also a nonspecific symptom, but not eating combined with lethargy means that the dog is bothered so much by their medical issue that they don’t want to eat and don’t have energy to be themselves. This should not be ignored for more than 24 hours.

Lethargic With Labored Breathing

Labored breathing is often a very serious symptom that needs to be recognized early. There is a difference between panting and labored breathing. With labored breathing, you will see your dog moving their belly muscles up and down rapidly and with force.

Labored breathing can be caused by several conditions that all need to be treated as soon as possible by a veterinarian:

  • Heart failure

  • Asthma

  • Fluid in the lungs or abdomen

  • Laryngeal paralysis (serious problem with the larynx)

  • Severe pain

  • Airway blockages

Lethargic and Drooling or Vomiting

If your dog is lethargic and drooling, it could mean they are nauseous or have ingested a toxin. It is important to check their environment to see if there is anything they could have gotten into. Drooling can progress to vomiting, which can have many causes.

Dogs can have an upset stomach if they eat something too rich for them (which can lead to serious pancreatitis) or swallow an object that gets stuck. If a dog is so nauseous that they are acting listless and uncomfortable, they definitely need to be seen by a veterinarian.

How Do Vets Treat Lethargic Dogs?

Your veterinarian will first perform a physical exam and check your dog’s gum color, hydration status, vitals with the heart and lungs, abdominal palpation, and spine and joint palpation.

Once they find where the problem may be coming from, they will recommend diagnostic tests, usually starting with bloodwork and x-rays. These tests will help the vet do a thorough check of all body systems and determine if there is something serious going on with your dog’s internal organs.

Sometimes the benefit of the tests is to rule out certain diseases or problems, and this is very valuable information. Just like human physicians, veterinarians cannot always determine an answer for every patient, but they know what to look for and how to make your dog as comfortable as possible.

They will offer specific treatments such as pain medicine, fluids if your dog is dehydrated, antibiotics if there’s an infection, or anti-nausea medicine if your dog is vomiting. It is always in your dog’s best interest to seek treatment early and not wait until they are severely ill and it becomes an emergency situation.

Featured image: iStock.com/Anna_Belova

Health Tools

Not sure whether to see a vet?

Answer a few questions about your pet's symptom, and our vet-created Symptom Checker will give you the most likely causes and next steps.

Stephanie Lantry, DVM


Stephanie Lantry, DVM


Dr. Lantry is a Milwaukee, Wisconsin native. She knew from a very young age that she wanted to be a veterinarian and worked towards that...

Help us make PetMD better

Was this article helpful?

Get Instant Vet Help Via Chat or Video. Connect with a Vet. Chewy Health