Lethargy in Cats

Because cats naturally sleep a large percentage of their day, especially older cats, you may not be immediately aware of lethargy indicating that something may be medically wrong with your cat. Lethargy is an indication of your cat not feeling well and could relate to a relatively minor medical condition or could be a sign of a more serious illness. Careful investigation by your veterinarian will be required to narrow down the cause.

Symptoms of lethargy in cats are abnormal sleepiness, low energy, and lack of response to surroundings. Lethargy is not a condition or disease in itself, but can be a sign that something is wrong with your cat. 

Lethargy is a symptom in itself and is characterized primarily by the following:

• General inactivity
• Lack of interest or response to surroundings
• Lack of energy
• Sleepiness or drowsiness

Other symptoms that commonly coincide with and are associated with causes of lethargy are:

• Weight gain
• Weight loss
• Diarrhea
• Fever
• Vomiting
• Thirst/increase in urination
• Jaundice
• Difficulty breathing
• Pain or discomfort
• Dull hair coat/loss of hair
• Behavioral changes, e.g. aggression

In addition, there may be specific symptoms present that are indicative of a specific medical disease or condition.

Cats sleep a lot by nature, however, excessive sleep or inactivity could be a sign of illness. Rest is your cat's natural response to not feeling well and could be a normal part of recovery from a minor condition or it could be an indicator of a more severe condition.

Common causes of lethargy:

• Being overfed, leading to obesity
• Being under exercised, leading to boredom and apathy
• Parasitic infection
• Stress
• Depression/too little stimulation
• Medication side effects
• Arthritis in older cats
• Hairballs (can become serious if causing blockage)
• Obesity
• Infection with a minor common virus such as cat flu

Other more serious conditions that are common in cats and cause lethargy are:

• Diabetes
• Viral infections such as feline immunodeficiency virus (FIV) or feline leukemia virus (FeLV)
• Bacterial infection 
• Abscesses from bites by other cats
• Musculoskeletal injury
• Heartworm
• Anemia
• Urinary tract infections

Less common but serious conditions that could cause lethargy in your cat are:

• Protozoal infections
• Cardiovascular disorders such as heart disease
• Respiratory problems resulting in low oxygen levels such as asthma
• Gastrointestinal disorders
• Heatstroke
• Cancer
• Organ failure (kidney or liver disease)
• Poisoning
• Neurological Disorders

Your veterinarian will perform a complete physical exam upon presentation of a lethargic cat. Diagnosis can be complicated as there are many possible causes of lethargy in cats which range from mild to severe, as lethargy is a symptom of many illnesses and disorders. Your veterinarian will require a complete medical history of your cat including detailed description of symptoms in order to narrow down a possible cause. In addition, you should let your veterinarian know about any changes to your cat’s environment or exposures they may have had recently. Your vet will look for injuries and abscesses, skin problems, swelling, and signs of pain or discomfort during the physical exam that may help determine the cause of the lethargy.

The following tests are commonly ordered to narrow down the cause of lethargy:

• Urinalysis and blood tests to check blood count, sugar levels and organ function. These tests can also look for factors that would indicate illness, bacterial infections, and viral infections
• Fecal sample to check for parasites
• Ultrasound to reveal visible abnormalities of organs or tumors
• Chest x-ray to reveal tumors or fluid buildup and to assess the cardiac silhouette
• FIV and FELV tests
• Heartworm tests

Treatment of lethargy will depend on the identified cause. General treatment of the symptom lethargy often includes an improved diet and supplements. It may also include intravenous fluids or oxygen therapy if required. Rest is also prescribed for lethargic cats that require it. Painkillers may also be prescribed if pain is a factor in your pet’s condition.

Common treatments prescribed for cats with lethargy according to their respective causes are:

• Antibiotics for bacterial infection
• Dewormer for parasites or heartworm
• Surgery for removal of tumors or to repair injury
• Antiviral medication for viruses
• Environmental changes and antidepressants for depression or stress
• Diet and insulin for treatment of diabetes

Further treatment specific to the cat’s medical condition will be prescribed as appropriate.

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Your pet will require follow-up care specific to the medical condition that was the cause of the lethargy.

Administration of any special diet and supplements prescribed by your veterinarian should be continued. If depression or stress were factors, a change to your cat’s environment may be needed to address this. 

A lethargic cat may be in need of recuperation and should be given a low stress, comfortable environment and be allowed to rest.