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My Dog Is Lethargic and Not Himself: What Should I Do?

When a dog is lethargic and not himself, it can be an immediate cause for concern. Any time our dog is acting unlike himself, we immediately think the worst and make plans to rush him to the vet even though it is sometimes not necessary.

How do we differentiate between an emergency and a simple tired day? What is lethargy in dogs to begin with? 

This article explains what lethargy in dogs is, why your dog might be lethargic, and how to determine if a Vet visit is necessary.

See also: When My Dog Died a Part of Me Died (6 Grieving Tips)

What Is Lethargy in Dogs?

Your dog might be lethargic if he moves slowly and appears drowsy, extremely tired, and uninterested in anything except lying around and resting.

dog lethargic not feeling himself

In some, this may be somewhat normal behavior due to already-diagnosed health conditions. In others, it is a cause for concern. 

Lethargy is a great indicator that there is something underlying going on with your pet. You don’t want to get up and do anything when you’re not feeling good, and neither does your pet.

While you should absolutely be alert anytime your dog is acting lethargic, you shouldn’t immediately jump to the worst-case scenario. 

What Causes Lethargy in Dogs? 

There are many different causes of lethargy in pets. Something as simple as a walk that was too long or a day that was just too hot can have a dog acting lethargic for the rest of the day or even potentially the next day.

French bulldog with allergies lying on the floor

This is normal and can be solved by rest, hydration, and a cool place to relax. You can learn more about how to keep your dog cool to stop overheating.

Your dog could also become more lethargic as they age, similar to how a human typically ages.

As they grow older and develop things like arthritis, their overall tolerance to activity decreases, and thus their need for rest increases. This is normal, but it shouldn’t suddenly happen all at once. 

Any very quick onset of lethargy with no known cause is an immediate cause for concern. This is especially true in younger animals.

If your brand-new puppy has suddenly started acting tired and not interested in playing at all, they need to see a vet. If they aren’t eating or drinking and are acting lethargic, they need to see the emergency vet. 

Conditions that could be contributing to a quick onset of lethargy in your dog include but aren’t limited to: 

  • Eye problems
  • Respiratory diseases (Kennel cough)
  • Joint problems (Arthritis)
  • Neurological disorders
  • Liver problems 
  • Digestive disorders 
  • Trauma 
  • Hypothyroidism
  • Cancer 
  • Pain
  • Poison
  • Diabetes
  • Dehydration 
  • Internal parasites

If your dog is acting lethargic, it does not mean that they automatically have one of the above conditions.

It is important, though, to ensure that you are prepared and act swiftly if they are displaying other symptoms or their lethargy has come on quickly. 

Medication Reactions 

Poor reactions to medications can also contribute to lethargy.

It is important to closely monitor your pet when starting them on anything new, including flea and tick or heartworm prevention medication. If you notice lethargy, get in touch with your vet quickly.

It is no surprise that a wide range of human medications are unsafe for our pets and that many can contribute to lethargy and, if not treated quickly, can even result in death.

You should call Animal Poison Control or rush your pet to an emergency vet if you suspect your pet has consumed any of your medications.

Always keep all of your medications out of your pet’s reach to avoid accidents. 


Dehydration can lead to lethargy in your pets the same way it leads to fatigue and lethargy in humans.

Frenchie panting

Similar to humans, animals’ bodies are made up primarily of water, and thus, they need a lot of water in order to function properly.

Things like dry kibble or hot weather may contribute to dehydration in dogs and thus result in lethargy. 

If you suspect that your dog is on the verge of dehydration, add water to their food and allow them to sip it down, and then add water once again.

Repeat this every time they eat so that they are getting a good amount of water in with every meal.

If your dog is not eating or drinking, or you suspect they’re severely dehydrated, it’s best to bring them to a vet where they can administer IV fluids to get them feeling better quicker.


Believe it or not, your dog can become depressed. Things like big life changes, consistent boredom, or a big loss can cause your dog to become depressed, which results in many symptoms of lethargy. 

dog depressed lying on the floor

If you have a high-energy breed dog and they’re not being utilized or exercised, they can become extremely depressed.

If you used to have two animals, but one passed away, its companion animal can become depressed.

Your pet may also suffer from depression if you recently moved houses, had a baby, allowed your boyfriend to move in with you, or had any other major life changes.

This doesn’t mean we should never change our lives; it just means we should pay attention to our pets and realize that sometimes their mental states can be as fragile as ours. 

If your dog has started to exhibit symptoms of depression, such as being less playful, not eating as much, or just isolating themselves, they may need some extra love and attention from you!

In the majority of cases, pets will adjust and go back to their normal selves within a few weeks after experiencing a major life change, but if they don’t, contact your vet to express your concerns. 

Poisonous Bites 

If your dog goes outside regularly without supervision and develops lethargy after coming in, it is possible that the lethargy can be attributed to a bite from another animal.

Things like poisonous insects and snakes can sometimes be undetectable by us, even in areas not surrounded by woods. 

If you think that there is a possibility that your dog was bitten by something poisonous, it is best to rush them to the vet right away.

In these situations, you can never be too safe, and it is better to exercise extreme caution because venom and poison can act very quickly and be fatal. 

Wrap-Up: Lethargy in Dogs

Many things contribute to lethargy in dogs and other animals. Some of these conditions require immediate vet attention, while others require simple monitoring.

If you’re unsure of what to do and stuck in the middle, the best course of action is to contact your vet for advisement and bring them in to be seen.

Though lethargy can be the result of something minuscule, it can also be an indicator that there is something seriously wrong.

Ensuring that your pet is seen quickly can be the difference between them being cured or developing even more serious symptoms, such as a dog that won’t eat or drink.

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Lisemaine is a dog lover. She currently owns two Frenchies and enjoys working with and training them. She'll share her best tips with you to keep your Frenchie happy, healthy, and active.

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