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Lethargy in dogs can be a sign of many different conditions in dogs. It’s what veterinarians refer to as a nonspecific sign, meaning that something is affecting your dog’s normal behavior, but that sign doesn’t necessarily tell you what’s wrong.

If you say to yourself, “My dog is lethargic and not himself,” you’ll have a pretty good idea of their current energy levels differ from their normal energy levels. Moreover, the behaviors you’ve observed might not be the same for your friend’s senior dog or your neighbor’s new puppy. Based on this information, you can work with your veterinarian to figure out what’s causing your dog’s lethargy and what, if any, treatments they need.

What Is Lethargy in Dogs?

Lethargy is defined as when your dog is less animated than usual or their activity level is “decreased from normal day-to-day function,” according to Dr. Amy Attas, VMD. “It’s a nonspecific sign, so it does not amount to a diagnosis.” Lethargy does indicate that something is making your dog feel unwell and it’s a good time to contact your veterinarian. Signs of lethargy vary considerably from one dog to another and include the following:

  • Tiredness or sleepiness
  • Low energy
  • Moving more slowly
  • Remaining inside their bed or crate
  • Reluctance to get up and play, move, and possibly eat
  • Not wanting to go for a walk
  • Unwillingness to do things they would normally do
©Eliška -

If you notice your dog lying down and not doing much, this might be normal behavior for a 13-year-old dog with arthritis, but a sign of lethargy for a puppy. But lethargy isn’t necessarily a function of age. If your senior dog goes on three walks a day and is now refusing to go out, you could describe them as lethargic. “There has to be a change in behavior compared to the dog’s baseline to say that they are lethargic,” Dr. Attas says.

How Does Lethargy Differ from Being Sleepy?

If your dog is sleepy, you can usually rouse them with their favorite treat. Or they might get up when they hear the doorbell. In contrast, a dog that is lethargic is probably feeling unwell, so it’s much harder for them to return to their normal behavior.

Another difference between lethargy and sleepiness is the length of time. If your dog is sleepy and they have a restful nap, they’ll probably wake up feeling better. “If they’re lethargic, sleeping doesn’t automatically make them feel better,” Dr. Attas says. “Fixing the problem makes them feel better and sometimes time itself fixes the problem.” If your dog’s condition doesn’t improve with sleep, you’ll need to identify and address the underlying cause.

Great Dane sleeping in the garden.
Sonja Birkelbach -

What Causes Lethargy in Dogs?

The causes of lethargy range from something relatively benign, like a bad night of sleep, to serious illnesses. In either case, the signs of lethargy can be similar. This is where your veterinarian will need to do some investigating to understand what is causing lethargy, such as:

  • Pain
  • Disease
  • Viral or bacterial infection
  • Reaction to a vaccine
  • The dog’s mental state
  • Effects of medication

Let’s imagine that a dog has a stomach virus or arthritis or recently underwent surgery. The dog might not want to get up and move around because they’re not feeling well. In contrast, if the cause is pain, nausea, or side effects of medication, the result might be lethargy, hence why it’s considered a nonspecific sign.

Can Allergies Cause Lethargy in Dogs?

Allergies themselves don’t usually make dogs lethargic unless they’re so severe that the dog doesn’t feel well, Dr. Attas explains. For instance, if your dog scratches to the point of causing a wound or infection, the dog might then become lethargic.

Can Antibiotics Cause Lethargy in Dogs?

Antibiotics can indirectly contribute to lethargy because they have the potential to make dogs feel unwell or nauseous, Dr. Attas says. If your dog starts taking an antibiotic and it upsets their stomach or gives them diarrhea, they’re likely to feel ill effects, including lethargy. If a dog is taking antibiotics and is acting lethargic, chances are the lethargy stems from the initial medical problem that the antibiotics are being used to treat.

animalinfo/Getty Images Plus

My Dog Is Lethargic, But Eating and Drinking

Lethargy doesn’t necessarily affect a dog’s appetite unless there are other symptoms like vomiting or diarrhea. “You can be really lethargic, but still maintain your appetite and have normal water drinking,” Dr. Attas says. When assessing lethargy, your veterinarian will likely ask if there have been any changes in your dog’s appetite or water consumption and if your dog is experiencing gastrointestinal (GI) upset. If your dog is having GI issues, lethargy can be a sign of an electrolyte imbalance, dehydration, or fever.

When Do You Need to Call Your Vet?

In situations where your dog is lethargic but showing no other signs of illness, your veterinarian might suggest waiting a few hours to see if the problem resolves on its own. If there is no improvement after 24 hours, your dog should see the vet for a full physical exam and bloodwork. Alternatively, if lethargy is persistent and accompanied by other symptoms like vomiting, you should find out what’s causing it because something is wrong, Dr. Attas says.

The bottom line is that lethargy isn’t a diagnosis. It’s important to know your dog’s normal activity level so you can tell when they’re becoming lethargic. “It’s better to err on the side of taking your dog to the vet so, if there is a serious problem, you get it taken care of as quickly as possible,” Dr. Attas says. “It helps to have a relationship with your veterinarian so that you feel comfortable contacting them if you think there is a problem.”

Related article: Aging in Dogs: Physical and Mental Signs Your Dog Is Getting Older
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