Why is My Dog Lethargic? | Causes & Treatments

Written by Crystal Moore | Last updated 18/09/24

If your dog is like mine, they're full of energy and absolutely loves it when it's time to go on a walk, and especially when he hears the treat jar open. As dog owners, we know what our furry friends are like, just like they know when it is time for their morning food and afternoon treat.

It becomes an increasing concern when your dog appears to suddenly lose all that energy and just sleep. They tend to appear unusually tired and weak, losing all interest in their adventurous walks and, in some cases, losing interest in their food. When this happens, it often indicates that your dog is lethargic, which could be a sign of an underlying health issue.

What is lethargy in dogs?

Lethargy is abnormal drowsiness and a state of reduced activity or sluggishness. When a dog is lethargic, they lack a lot of energy and tend to become uninterested in activities they would've enjoyed before. This can be walks, playing in the garden and in some cases, lethargic dogs can become uninterested in their food and treats.

Temporary lethargy in dogs can be a result of extreme weather, such as high temperatures, or a high-intensive activity. Furthermore, lethargy can be a symptom of different health issues such as infections, illnesses, liver disease, pain, anxiety, dehydration, or medication side effects.

What is the difference between a lethargic and tired dog?

There is an important difference between a dog that is lethargic and a dog that is tired. A lethargic dog tends to have reduced activity levels as well as showing little to no interest in their daily activities. In some cases, they may become uninterested in their regular meals and their favourite dog treats. A lethargic dog might act out of character and sleep excessively.

On the other hand, a tired dog will still act like themselves. They tend to be less active and will prefer to sleep, over playing. However, when they've been awoken, they'll be up and ready for anything.

Causes of lethargy in dogs

There are various causes of lethargy, which can affect dogs of all ages. Lethargy is a sign for almost all conditions, such as infections, illnesses, pain, and medication, making lethargy a reasonably common symptom to see.

Infections

Any infection can cause your dog to be lethargic due to the immune system working hard to fight off the pathogens. Some infections can cause a fever, pain or reduced appetite. With more severe infections, it can have systemic effects that impact various body systems. Each of these symptoms of an infection can greatly impact a dog's activity levels and cause them to be lethargic.

Some of the most common infections that cause lethargy in dogs are kennel cough, parvovirus, distemper, Lyme disease and urinary tract infections.

Illnesses

If a dog has an illness, it affects their body's normal function and usually affects multiple or all body systems. Due to the illness, it can directly or indirectly cause discomfort which takes a toll on their energy levels. It is crucial that you contact your veterinarian if you discover additional symptoms alongside the signs of lethargy. Your vet will be able to diagnose and treat any underlying health conditions that your dog may have.

Illnesses such as diabetes mellitus, hypothyroidism, heart disease, kidney issues, liver disease, and cancer can make your dog lethargic.

Pain or trauma

Pain and trauma can be both internal or external injuries that cause a dog a lot of discomfort, leading to a decrease in movement, especially if they're trying to avoid worsening the pain. There are other signs of pain, such as a change in your dog's behaviour, licking at the area in pain, and a lot of time spent resting.

Likewise, if a dog has pain due to periodontal disease, they are most likely to eat less or lose their appetite entirely. When a dog has chronic pain or trauma, the dog's body can be forced to conserve energy. Due to this, the dog can become lethargic. If you notice your dog is in pain or discomfort, contact your veterinarian immediately to ensure their overall well-being.

Medication

There are certain medications for dogs that can cause lethargy and weakness. These symptoms can be a side effect of the medication or, the medication might contain sedative properties that are often prescribed to manage pain, anxiety or other conditions. The sedative properties in these certain medications can cause a dog to become drowsy.

Nevertheless, speak with your veterinarian as soon as you notice your dog becoming weak or lethargic after taking the medication. Your vet will be able to check if everything is correct, or if the medication might need to be adjusted or changed.

Poisoning

Poisoning can occur when your dog ingests something that is toxic to them, such as chocolate, onions and toxic plants. When these poisons enter the body, it can disrupt the normal bodily functions by interfering with the metabolic processes. As your dog's body tries to fight away the toxins, the shock and stress of it all can greatly reduce your dog's energy levels and cause your dog to be lethargic. Seeking veterinary care immediately is vital to minimise the effect. If left untreated, it can negatively impact your dog's health and, at worst, cause death.

Other causes

Nutritional deficiencies
Dehydration
Heatstroke
Chronic diseases

Should I be concerned if my dog is lethargic?

Lethargy isn't much of a concern when it is mild. There may be a reasonable explanation such as they've finished an activity that required them to exert a lot of energy, or the temperatures outside are very hot. Lethargy becomes a concern when it is moderate to severe. A veterinarian should be contacted when you're no longer able to get your dog's attention or when other symptoms are present.

Additional symptoms to look out for:

Behaviour changes
Shivering
Difficulty breathing
Rapid breathing
Vomiting
Diarrhoea
Drooling
Loss of appetite
Increased thirst

When to seek veterinary guidance

Your veterinarian should be contacted if you suspect the cause of your dog's lethargy is due to a health issue. Additionally, you should visit your vet as soon as possible if you start to notice any other symptoms, such as changes in behaviour, lack of appetite, diarrhoea, and difficulty breathing. It's likely that your dog's lethargy is caused due to an underlying health condition if additional symptoms are present.

What are the treatments for lethargy in dogs?

Before any diagnosis is made, the veterinarian will begin by asking you a range of questions regarding any past health concerns, your dog's recent behaviour and activity levels. The vet will need to perform a thorough physical examination and carry out additional diagnostic tests on your dog's urine, faeces, and blood. If there is a concern with your dog's heart, x-rays, ultrasounds, or any other imaging techniques might need to be conducted in order to get a clearer image.

Frequently Asked Questions

Why is my dog walking so slow and looks weak?

If your dog is walking slowly and appears weak, it could be due to various underlying health issues, ranging from pain, illness, or injury to fatigue from strenuous activity. Weakness and slow movement can be signs of pain in their muscles or joints, such as arthritis, or it could indicate an underlying health condition like heart disease, dehydration, or an infection.