Fever in Cats


Fever, or pyrexia, is an increased body temperature, surpassing 102.5 °F (39.2 °C) in cats. The rise in temperature occurs when the body adjusts its internal temperature set point as a physiological response to illness or injury. 

A fever can be caused by a wide array of diseases and conditions. It is most commonly the result of the body’s natural defense mechanism after viral or bacterial infections. 

Body temperatures in excess of 103F° (39.4 °C) warrant veterinary attention if the fever persists for more than 24 hours. 

If the cat’s temperature surpasses 105F° (41 °C), this is an emergency. Body temperature this high poses a serious risk of damage to tissues and vital organs. 

Taking a cat's temperature may not be easy for inexperienced pet owners and a trip to the veterinarian may be the safest way of knowing with certainty if the cat has a fever. If a fever is suspected (or confirmed) veterinary attention is recommended to determine the root cause. 

Treatment and prognosis vary in accordance with the underlying cause of the fever. It is recommended to check with a vet if a cat is suspected of having fever before administering any medication. Never give human medication to a cat, as many human medications such as paracetamol are very toxic to cats.


Fever is not necessarily a concern in and of itself. In some cases, such as specific types of infections, it may be advantageous to let the fever run its course. In these cases, it is wise not to suppress the fever  

If a cat exhibits a fever of 103F° (39.4 °C) for more than 24 hours, veterinary attention is advised. Higher fevers warrant more urgent veterinary care. Fevers over 104.5 °F (40 °C) are an emergency

Fevers are often accompanied by other symptoms that may also indicate an emergency, including: 

• Labored breathing (dyspnea) • CollapseSeizures

Possible Causes

Fever is generally associated with many different feline conditions, disorders, and syndromes including:

• Bacterial infections, particularly bite wound abscesses

• Viral infections such as FeLV,  FIV, and feline infectious peritonitis (FIP)

• Trauma and injury • Dental infection • Upper respiratory tract infection • Poisoning • Tumor and cancers

Risk Factors

Outdoor cats are more likely to contract a virus or infection associated with fever. Fever varies greatly in severity depending on the underlying condition causing the increased body temperature. Some fevers are beneficial.

Mild fever: Cats with a mild fever (103°F (39.4 °C)) may exhibit lethargy and lack of appetite. Temperatures lower than 103 °F (39.4 °C) are not expected to cause permanent damage.

Moderate fever: Body temperatures ranging from 103 °F (39.4 °C) - 104.5 °F (40 °C) put a cat’s tissues at risk of damage. Fevers in this range typically indicate more serious underlying causes that warrant urgent veterinary attention.

High fevers over 104.5 °F (40 °C) are an emergency. Fevers over 106 °F (41 °C) are life-threatening.

Testing and Diagnosis

The initial diagnosis is carried out by taking the cat's temperature. The most accurate method is by way of a digital rectal thermometer. If a veterinarian confirms that a fever is present, the following diagnostics are typically performed: 

• Physical examination • Blood work • Urinalysis • Diagnostic imaging

If the cause of the fever can not be ascertained and the fever persists, the cat is categorized as having fever of unknown origin (FUO).

Treatment varies widely depending on the root cause. Symptomatic treatment often involves fluid administration (IV or subcutaneous), anti-inflammatories, and/or antibiotics.  

In the case of lower fevers, treatment does not usually include efforts to lower the cat’s body temperature because the fever may help the cat fight off the infection. Bite wound abscesses may require minor surgery for lancing and flushing.

Similar symptoms

Hyperthermia caused by heat exhaustion or heat stroke may be mistaken for fever. Note: heat exhaustion can rapidly develop into heat stroke, which is life threatening. Always take steps to reduce symptoms of heat exhaustion as soon as they appear.

Associated Symptoms

A cat suffering from fever may present several additional symptoms, including but not limited to:

• Loss of appetite • Lethargy • Pain • Swollen bumps in the skin  • Open, draining sores• Lameness • Runny eyes

• Nasal congestion • SneezingDiarrhea • Vomiting

Want to speak to a vet now?

Book an appointment

Health concern with your pet?

Start a video chat with a licensed veterinary professional right now on Vetster!

Book an online vet