Lethargy in cats


Lethargy can be defined as having decreased energy and lowered levels of activity. It is a difficult symptom to identify in a cat, since cats typically are not highly active animals and tend to spend much of the day at rest. Lethargy may be noted when a cat stops moving around the house or playing as they usually do. Lethargy is easily overlooked in cats if it is the only symptom present.

Essentially any type of illness or injury has the potential to cause lethargy in a cat.    Lethargy is often normal, especially if it is mild, temporary, and unaccompanied by other symptoms. When assessing a lethargic cat, it is important to look at how profound the lethargy is, how long it has been going on for, if it is intermittent, and if there are any other symptoms noted. Lethargy does not typically indicate an emergency unless other symptoms are present. Diagnosing a lethargic cat usually requires a thorough diagnostic workup including a physical examination, bloodwork, urinalysis, and diagnostic imaging. 

Treatment is dependent on the underlying condition.


Lethargy is a very common symptom in cats and it is seen with a variety of illnesses and injuries. There is a short list of conditions where a cat would not be expected to display lethargy, including ingestion of a stimulant, chocolate toxicosis, and hyperthyroidism.

Lethargy is expected under some circumstances, such as during the decrease in activity seen with many aging cats or when a cat who is recovering from a stressful event or long play session. 

If lethargy is accompanied by symptoms of an emergency, like collapse, paralysis, seizure activity, difficulty breathing or difficulty urinating, emergency veterinary care is warranted.

Possible Causes

A cat may be lethargic for a multitude of reasons. In some cases, such as after exercising, lethargy is normal and temporary. More serious conditions associated with lethargy include:

• Heat stress • Infection • Parasites • Poisoning • Hormonal disorders • Nutritional disorders

• Liver or kidney disease • Heart disease • Respiratory disease • Urinary tract infections

• Gastrointestinal disorders • Inflammatory diseases • Immune-mediated diseases • Cancer

Risk Factors

It is difficult to accurately identify or assess lethargy in cats since they spend a lot of time sleeping when they’re healthy. Lethargy is described according to these characteristics: 

• Severity • Duration  • Frequency • Context: Did anything happen in association with the onset of the lethargy

• Presence of other symptoms

Testing and Diagnosis

Diagnosing the cause of lethargy in cats is challenging since there are many potential conditions that lead to this symptom. 

After taking a thorough history and performing a physical exam, typical diagnostics include: 

• Bloodwork • Urinalysis • X-Rays

Similar symptoms

Lethargy is difficult to distinguish from other poorly defined symptoms like reluctance to move and fatigue. In some cases it may be mistaken for an episode of collapse or fainting.

Associated Symptoms

Lethargy is commonly seen along with nearly all symptoms of illness or injury. Lethargy as a solitary symptom in a cat is unlikely to be significant.

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