Lethargy in dogs is typically a symptom associated with a larger underlying health issue. Determining the underlying clinical factors driving your dog’s lethargy is key to formulating a treatment plan that will lead to their recovery.

Key Takeaways

  • There are many reasons why your dog could suddenly be lethargic. These can include bacterial infections, viruses, cancer, and pain.
  • You can give your dog water, feed them a bland a diet, and put them in a space where they can get rest.
  • Dogs can recover from lethargy with adequate treatment.
  • Call the veterinarian if your dog is lethargic and has a low or high temperature, if they are panting and restless, their gums are pale, their stomach feels bloated, they haven’t eaten in a day, or they are vomiting, drooling, or have diarrhea.
  • How long lethargy lasts depends upon what is causing it, so take your dog to the veterinarian if you are concerned.

What is Lethargy?

Lethargy is excessive sleepiness, lack of energy, or weakness. Lethargy can shift your dog’s entire personality, alter their daily routine, and cause them to lose interest in their favorite activities. Lethargy in dogs is typically associated with an overall decrease in activity. For example…

  • Your dog may engage in normal activities but with less “spunk.”
  • Your dog may only move to take care of the essentials, like going to the bathroom.
  • Your dog may walk around the house without engaging in normal activities.
  • Your dog may not want to play.
  • Your dog may have bursts of physical activity that are followed by an energy crash.
  • Your dog may be interested in eating, but take longer to eat, only sniff or lick their food, or turn their head away when food is offered.
  • Your dog may not show interest in you, other people, or their surroundings.

Dogs experiencing lethargy are not their usual selves, and this may result in some obvious shifts in their behaviors, including those associated with interest, affection, and play.

Is It Lethargy, Or Is Your Dog Just Tired?

Just like us, dogs get tired. But a tired dog is typically ready for action as soon as they’re well-rested.

For example, a healthy dog may have an energetic reaction when you grab their leash. Alternatively, a lethargic dog will have little to no reaction or will act interested only to quickly lay back down.

What Causes Lethargy in Dogs?

Lethargy is what is called a “non-specific” sign in dogs. A non-specific symptom can show up in many illnesses and problems. Your dog’s lethargy might be caused by more than one illness, so your veterinarian’s priority is finding out what is going on and treating that problem.


Dogs who are immunosuppressed because of cancer, cancer treatment, or another illness are more at risk for picking up viruses and developing bacterial infections.

  • Viruses, like parvovirus and those that cause upper respiratory tract infections, can enter your dog’s body. This can happen by being in close contact with other dogs who are sick.
  • Bacterial infections can be dangerous for immunocompromised dogs because their body is not as capable of fighting it off. Your dog may or may not develop a fever in response to a bacterial infection.
  • Urinary tract infections are more likely if your dog does not regularly urinate or drink enough water.
  • Leptospirosis is a blood infection caused by the bacteria Leptospira. Your dog can get leptospirosis by contacting the urine of other infected animals, like raccoons.
  • Your dog’s anal glands can become infected if they become impacted and cannot be expressed. This makes it very painful for them to defecate.
  • Gastrointestinal bacterial infections, like salmonella, can be problematic. They can cause gastroenteritis, or inflammation of the stomach, and sepsis, which occurs when an infection enters the bloodstream. This is a large reason why dogs with cancer should not be given raw meat.1
  • Skin infections and ear infections can also be taxing for immunocompromised dogs. These typically have to become severe before they become dangerous. Of course, you still want to seek treatment if you suspect your dog is suffering from them.

Cancer and Cancer Treatment

Lethargy is a common side effect of certain cancers, medications, and therapies.

  • Lymphoma and gland carcinoma are highly associated to hypercalcemia.2 Hypercalcemia is a condition whereby the level of calcium in the blood is too high. This can cause lethargy.
  • Your dog’s bone marrow may become suppressed due to their cancer or cancer treatment. This is called myelotoxicity. Bone marrow plays a large role in making new red blood cells, so reduced function can lead to anemia over the course of several weeks. In dogs, its associated with Sertoli cell tumors4 as well as use of the chemotherapy drug carboplatin.5


Anemia can also cause lethargy. Anemia is when the body has a reduced number of red blood cells. It can result from loss of blood. Anemia can be chronic in that your dog’s body does not make enough healthy red blood cells to begin with. Renal disease is also linked to anemic outcomes for dogs that have the condition.

Heart Issues

Lethargy may be caused by heart issues, such as arrhythmia, an irregular heartbeat, or congestive heart failure brought on by fluid buildup in the lungs. Cardiac issues can result from tumors that are associated with the heart, although these are highly uncommon.6

If your dog receives the chemotherapy drug doxorubicin, then outcomes as severe as heart failure may occur depending on your dog’s tolerance to the medication.7

Pain Is a Common Cause of Lethargy

Pain is our brain’s way of telling us that something is wrong with our bodies. But just like some humans are stoic, dogs can be too.

Dogs are similar to their wild ancestors. They are apt to hide signs of pain to avoid showing any signs of weakness. But when pain gets too intense, it can cause them to not want to move too much.

  • Cancers are notorious for causing pain. Pain may be caused by microfractures or fractures resulting from osteosarcoma3 or trauma. Abdominal pain due to the presence of a mass in the nearby area, or due to strain on the blood supply and nerves could be causing pain.
  • Cancer treatments can also be painful. Chemotherapy and radiation can be tough on your dog’s body. Veterinarians will commonly prescribe medication for pain management post-treatment for this reason.
  • Other conditions not related to cancer, such as pancreatitis or an ear infection, can subsequently cause pain that leads to a lethargic condition.

Many Other Causes of Lethargy

This list of factors that contribute to lethargy can go on and on. Your dog may be dehydrated, have glucose levels that are too low or too high, suffer from hypothyroidism, or may be undergoing neurological issues such as geriatric vestibular syndrome.

How to Assess Lethargy in Dogs at Home

Is it lethargy? Check the following:

  • Start by taking your dog’s temperature. It should range between 99 to 102.5°F. Make sure that the environment you take your dog’s temperature in is normal. For example, your dog shouldn’t be laying in the sun. A temperature reading under 99°F or over 102.5°F warrants a visit to the vet. Even if your dog’s temperature is normal, it’s a good idea to take it again every few hours.
  • Gently touch your dog’s stomach. Determine whether or not it feels bloated. If so, call your veterinarian.
  • Assess their gums. A healthy dog will have pink gums that are a salmon color and moist to the touch. Unhealthy dogs will have gums that are pale or purple and “tacky” feeling.
  • Check their breath rate and degree of panting. Your dog should take approximately 15 to 30 breaths per minute. Excessive panting or breaths numbering over 30 per minute is cause for concern. Likewise, labored breathing also means you should contact your vet.
  • Reflect on your dog’s overall attitude at present and of late.
    • Have they been lying down completely flat?
    • Do they appear to be interested in what is going on around them?
    • Have they been restless?
    • Have they been drinking and eating?
  • Offer your dog their favorite treat. Whether or not they accept it may be indicative of their appetite and level of interest in once highly rewarding experiences.

When to Call Your Vet

To recap the list above and add on some other considerations, here’s when you should call your veterinarian or pet emergency hospital:

  • If your dog’s temperature is under 99°F or over 102.5°F.
  • If your dog’s respiratory rate is over 30 breaths per minute, or if their breathing is labored, or if they are excessively panting and restless.
  • If your dog’s gums are pale, purple, or sticky to the touch.
  • If your dog’s stomach feels bloated.
  • If your dog is clearly acting lethargic, is shaking, or restless.
  • If your dog is lethargic and has not eaten for 24 hours.
  • If your dog is lethargic and is also experiencing vomiting, especially more than one to two times within 24 hours, diarrhea, or abnormal levels of drooling.

Trust your instincts, you know your pet better than anyone. If you are wondering whether or not you should call your veterinarian, the answer is likely yes.

Things that Help Treat Your Dog’s Lethargy

Focus on keeping your dog hydrated. You can try giving them cold water, warm water, ice cubes, bone broth warmed up or frozen into ice cubes, as well as goat’s milk refrigerated or frozen into ice cubes.

Keep your dog’s diet bland. You can offer them 50% boiled chicken and 50% canned pumpkin, or 50% boiled chicken and 50% boiled rice. Modify as appropriate and keep your dog’s allergies in mind. Bland diets are not balanced and cannot be used long term, but they can help get some symptoms that may be contributing to lethargy under control.

Encourage your dog to sleep. Give them an environment conducive to rest. Remove them from spaces with other dogs, kids, and people. The only disturbance your dog should experience is you coming to regularly check in on them.

Is Lethargy in Dogs a Sign They Are Dying?

Lethargy has a multitude of causes and is indicative of a larger health issue going on with your dog.

This doesn’t mean that your dog is nearing the end of their life. Many of the drivers of lethargy can be treated and lead your dog to a full recovery. The key is gathering as much information as possible to accurately determine the underlying cause and shape an effective treatment plan.

  1. Dressler D, Ettinger S. The Dog Cancer Survival Guide. Maui Media; 2011.
  2. Bergman PJ. Paraneoplastic hypercalcemia. Top Companion Anim Med. 2012;27(4):156-158. doi:10.1053/j.tcam.2012.09.003
  3. Tilley LP. Blackwell’s Five-Minute Veterinary Consult: Canine and Feline. Oxford, UK: Wiley-Blackwell; 2011, pp923-924, 544-545.
  4. Salyer SA, Lapsley JM, Palm CA, et al. Outcome of dogs with bone marrow suppression secondary to Sertoli cell tumour. Vet Comp Oncol. 2022;20(2):484-490. doi:10.1111/vco.12794
  5. Giuliano A, Almendros A. Retrospective Evaluation of a Combination of Carboplatin and Bleomycin for the Treatment of Canine Carcinomas. Animals (Basel). 2022;12(18):2340. Published 2022 Sep 8. doi:10.3390/ani12182340
  6. Treggiari E, Pedro B, Dukes-McEwan J, Gelzer AR, Blackwood L. A descriptive review of cardiac tumours in dogs and cats. Vet Comp Oncol. 2017;15(2):273-288. doi:10.1111/vco.12167
  7. Vaynblat M, Pagala MK, Davis WJ, et al. Telemetrically monitored arrhythmogenic effects of doxorubicin in a dog model of heart failure. Pathophysiology. 2003;9(4):241-248. doi:10.1016/s0928-4680(03)00026-9



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