What Causes Dog Diarrhea And Lethargy?

If your dog has diarrhea and lethargic at the same time, we outline the potential causes of dog diarrhea and lethargy, as well as what to do and when to seek help. 

Here’s why dog diarrhea and lethargy occurs

Dog diarrhea and lethargy are symptoms that commonly occur together can be caused by a number of illnesses and disorders which includes gastrointestinal infections, diet, food allergies, medication side effects, illness, stress, and poisoning.

Dog diarrhea and lethargy

Dog diarrhea and lethargy

Lethargy in dogs is characterized by a lack of energy, weakness, and an overall feeling of tiredness. 

Signs of lethargy in a dog manifests as a lack of interest in activities that they previously enjoyed, such as playing or going for walks, and can also be accompanied by a lack of appetite, and difficulty standing or moving.

It can be a symptom of an underlying condition, both acute and chronic conditions.

Dog diarrhea on the other hand is a condition in which a dog’s stool is loose and watery, and which they pass more frequently than normal. 

Occasional episodes of diarrhea in dogs are common and normal, however, frequent diarrhea as well as other concerning symptoms can be a sign of a serious underlying problem.

Diarrhea and lethargy happening at the same time can be due to a variety of causes. In most cases, these symptoms are accompanied by other symptoms such as vomiting, loss of appetite, lethargy, and fever.

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Possible causes of dog diarrhea and lethargy

Diarrhea and lethargy happening at the same time can have a variety of causes due to an underlying condition. 

The possible causes of diarrhea and lethargy are:


Diarrhea and lethargy can be symptoms of a wide range of illnesses in dogs, including viral or bacterial infections, gastrointestinal disorders, and systemic diseases.

These diseases and conditions include parvovirus, distemper, kidney or liver disease, inflammatory bowel syndrome, colitis, or cancer.

Gastrointestinal infection

Gastrointestinal infection by bacteria, intestinal parasites, or viruses is the most common cause of diarrhea and lethargy in a dog.

Infections of the digestive tract cause inflammation and irritation, leading to diarrhea and lethargy. Some common symptoms of gastrointestinal infections include vomiting and loss of appetite.

Bacterial infections include Salmonella, coccidia, or Escherichia coli (E. coli) while viral infections include parvovirus and parasitic infections can be from roundworms, hookworms, tapeworms, and whipworms.

Change in diet

A change in your dog’s diet can cause diarrhea and lethargy due to food intolerance or allergy, an upset stomach, and stress.

This is because it takes time for your dog’s stomach to adjust to the new food and a sudden change to a new food may cause diarrhea. 

Dogs are also sensitive to changes in their routine and environment, and a sudden change in diet can be stressful. This stress can lead to digestive upset and other symptoms such as lethargy.

To avoid these problems, it is important to introduce changes to your dog’s diet gradually, over the course of several days or weeks, to give their digestive system time to adjust.

Also, it is important to choose a high-quality, nutritionally balanced dog food that meets your dog’s individual needs.


A stressed dog also experiences diarrhea including lethargy, which may appear at the same time. 

Stress and anxiety also cause a variety of symptoms including pacing, licking, drooling, yawning, crying, barking, and hiding.

Stress can come from a variety of sources such as a change in their environment or routine, new people or pets, loud noises, and other fear-related stressful situations.

Related: Dog diarrhea and pacing: Here’s why

Toxin ingestion

Poisoning in dogs can lead to a variety of symptoms, including diarrhea and lethargy. This is because many poisons and toxins can cause gastrointestinal upset and also affect the nervous system.

Dogs may accidentally ingest toxic substances such as household cleaners, contaminated food or water, pesticides, insecticides, poisonous plants, or human medications, which can cause diarrhea and other symptoms.

Side effects of medication 

Medications can sometimes cause side effects in dogs, including diarrhea and lethargy which may happen at the same time.

The side effects can occur due to irritation of the digestive tract, and allergic reaction which causes lethargy.

Related: Understanding dog diarrhea and limping 

Dietary indiscretion

Dietary indiscretion refers to eating non-food items or food that is not part of a dog’s regular diet. This can lead to diarrhea and lethargy in dogs due to the development of an upset stomach, bacterial or viral infection, gastrointestinal obstruction, and stress.

Dogs may eat non-food items or consume food outside of their regular diet due to stress or anxiety, which can also lead to digestive upset and other symptoms such as lethargy.

Dog diarrhea and lethargy: What to do 

If your dog is experiencing both diarrhea and lethargy, it is important to seek veterinary care as soon as possible. 

Here are  other signs that indicate that you should see a veterinarian immediately:

Severe or bloody diarrhea: If your dog’s diarrhea is severe or if there is blood or mucus in the stool, this could be a sign of a serious underlying condition and requires immediate veterinary attention.

Other symptoms: Other symptoms may accompany diarrhea and lethargy, such as vomiting. If your dog is vomiting along with diarrhea, this can lead to dehydration and other complications and requires immediate medical attention. 

Other symptoms to look out for include lack of appetite, breathing difficulties, signs of pain or discomfort, fever, and signs of dehydration, such as a dry nose or mouth and sunken eyes.

Suspicion poisoning: If you suspect that your dog has been poisoned, it is important to seek veterinary care immediately.

If your dog is a puppy or an older dog: Puppies and older are generally more vulnerable than healthy adult dogs so delaying treatment could result in their condition worsening or becoming more difficult to treat. Therefore, it is essential to seek immediate medical care.

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Key Takeaway: Dog diarrhea and lethargy

Diarrhea and lethargy in dogs can be caused by a variety of factors.  While occasional diarrhea is normal in dogs, persistent diarrhea alongside other symptoms such as lethargy requires veterinary attention.

If you notice your dog showing these symptoms suddenly or for extended periods of time, consult with your veterinarian to determine the underlying cause and appropriate treatment. 

By addressing the underlying cause of the symptoms and providing appropriate care, you can help ensure that your dog remains healthy.

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