My Dog Has Diarrhea And His Back Legs Are Weak: Here’s Why

It is incredibly concerning when your dog has diarrhea and his back legs are weak. Dog diarrhea with weak back legs is a clear indication of a problem.

We outline the potential causes of dog diarrhea and weak back legs as well as what to do and when to seek help. 

Here’s why your dog has diarrhea and his back legs are weak

Dog diarrhea and weak back legs are symptoms that can be caused by underlying health problems which includes dehydration, poisoning, gastrointestinal infections, and neurological conditions.

My dog has diarrhea and his back legs are weak

Common Causes of Dog Diarrhea and Weak Back Legs

Common causes behind dog diarrhea with weak back legs include:


Dehydration itself does not directly cause diarrhea or weak back legs. However, severe dehydration can lead to electrolyte imbalances and other physiological changes that can contribute to these symptoms indirectly.

Diarrhea can lead to dehydration, which often leads to electrolyte imbalances. Electrolytes play a crucial role in muscle function and nerve transmission.

When electrolyte levels are disrupted, it can affect muscle contraction and coordination, potentially leading to weakness in the back legs.

Dehydration can also cause overall weakness and fatigue in a dog. When the body lacks sufficient fluids, it can affect energy levels and muscle strength, including the muscles in the back legs. 

This weakness may show as difficulty standing, walking, or supporting the weight of the body.


Poisoning in dogs can lead to various symptoms, including diarrhea and weak back legs. The specific effects and severity can depend on the type of toxin ingested.

Poisoning can cause dog diarrhea and weak back legs through:

Systemic Toxicity: Some poisons can have systemic effects on a dog’s body, including the muscles and nervous system. 

The toxins can interfere with nerve signaling and muscle function, leading to weakness, including weakness in the back legs. The severity of the weakness can vary depending on the specific toxin and the extent of exposure.

Gastrointestinal Irritation: Many toxic substances can irritate the gastrointestinal tract, leading to inflammation and disruption of normal digestive processes. 

This irritation can cause diarrhea as the body tries to eliminate the harmful substance. The diarrhea may range from mild to severe, depending on the toxicity and dose of the ingested toxin.

Organ Damage: Certain toxins can cause damage to vital organs, such as the liver or kidneys, which are responsible for filtering toxins from the body. 

When these organs are affected, it can lead to systemic effects, including weakness and diarrhea. 

Dehydration and Electrolyte Imbalance: Some toxins can cause vomiting or increase in  fluid loss through other means, such as increased urination. 

This can lead to dehydration and electrolyte imbalances, which can lead to weakness including  weakness in the back legs.

Related: Dog Diarrhea and shaking: Causes and What to do

Gastrointestinal Infections

A gastrointestinal infection can cause diarrhea and, in some cases, weak back legs in dogs.

A gastrointestinal infection itself typically does not directly lead to weak back legs in dogs. However, in some cases, certain complications associated with gastrointestinal infections can indirectly contribute to weakness in the back legs.

This includes dehydration and electrolyte imbalance caused by the infections due to diarrhea and vomiting. Dehydration, especially when severe, can lead to weakness and lethargy, which can affect the overall strength and coordination of the dog, including the back legs.

Gastrointestinal infections can also cause abdominal pain and discomfort in dogs. When a  dog is in pain, they may show signs of weakness and reluctance to move or use their back legs normally. 

The pain can result in a temporary decrease in mobility and coordination until the infection and associated symptoms are resolved.

Neurological Conditions

Certain neurological disorders, such as degenerative myelopathy or intervertebral disc disease, can cause both diarrhea and weakness in the hind legs. 

These conditions affect the nerves responsible for muscle control and coordination.

Not all neurological disorders directly cause diarrhea or weak back legs. However, they can be associated with these symptoms due to the complex connections between the nervous system and various body functions.

What to do when your dog has  diarrhea and his back legs are weak

If your dog is experiencing both diarrhea and weak back legs, 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 shaking, 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 lethargy, 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.

Key Takeaway: Dog diarrhea and weak back legs

Diarrhea and weak back legs in dogs can be caused by a variety of factors.  While occasional diarrhea is normal in dogs, persistent diarrhea alongside other symptoms 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 and happy.