Fever in cats

Author: Dr. med. vet. Gisa Löwe | Last modified: 17.02.2026
Table of contents

When to visit the vet?

Urgent see a veterinarian within 24 hours

?

RED in case of shortness of breath, collapse, seizures, significant apathy, dehydration, or very young/old/immunosuppressed cats (e.g., FeLV/FIV).

Unsure about what’s wrong with your pet? Feel free to use our Symptom Checker for more clarity

Definition

Fever in cats is an increase in body temperature above the normal range, which is typically between 38.0°C and 39.2°C. Values above 39.2°C are considered a Fever.

Can Occur with the Following Diseases:

Basics and possible causes

Fever is a natural reaction of the body to pathogens such as bacteria, viruses, or fungi. It can also be triggered by Inflammatory conditions, injuries, or certain medications. The body raises its temperature to support the immune system by inhibiting the reproduction of microorganisms and increasing the activity of immune cells.

The causes of Fever in cats are diverse. Infections are one of the most common causes. Bacterial infections, such as respiratory or urinary tract infections, can cause Fever. Viral infections like Feline Calicivirus or Feline Herpesvirus are also frequent triggers. Fungal infections, though rarer, can also cause Fever.

Non-infectious causes should also be considered. These include autoimmune diseases, where the immune system attacks the body’s own tissues, as well as cancers. Reactions to vaccinations or the intake of certain medications can also occasionally trigger a Fever. In some cases, the exact cause remains unknown; this is referred to as “fever of unknown origin.”

Typical accompanying symptoms

  • Lethargy: Cats with a Fever often seem tired and less active than usual. They withdraw and sleep more than they normally do.

  • Loss of appetite: A feverish cat often eats less or refuses food entirely. This is a common reaction of the body to illness.

  • Dehydration: Due to the increased body temperature, fluid loss (dehydration) can occur, which can lead to dehydration. This is shown by dry mucous membranes and skin that slowly returns to its original position when lifted.

  • Rapid breathing or Panting: A feverish cat may breathe faster to regulate its body temperature. Panting is unusual in cats and should always be considered a warning sign.

  • Changes in behavior: Cats with a Fever can be irritable or restless. Some withdraw, while others seek more closeness than usual.

  • Chills: Cats may show shivering or muscle tremors as the body attempts to raise the temperature further.

When to see a vet?

A visit to the vet is urgently required if the Fever lasts longer than 24 to 48 hours or if the temperature exceeds 40°C. Such high temperatures can lead to serious health problems and require immediate medical treatment.

A vet should also be consulted if the Fever is accompanied by other symptoms, such as severe Vomiting, Diarrhea, jaundice (yellowing of the skin or eyes), or signs of Pain. These symptoms can indicate more serious health issues.

Young kittens, older cats, or cats with a weakened immune system are particularly vulnerable to the effects of Fever and should be medically examined at the first signs.

Symptom recognition for the pet owner and veterinary diagnostic procedure

Pet owners can detect a Fever by measuring their cat’s temperature with a rectal thermometer. Digital thermometers are the easiest to use and provide fast results. A temperature above 39.2°C indicates a Fever.

At the vet, a thorough medical history will be taken to identify possible causes for the Fever. The vet will physically examine the cat to identify signs of inflammation or other symptoms. Blood tests may be necessary to diagnose infections, Inflammatory conditions, or other health problems.

In some cases, further tests such as X-rays, ultrasound, or special blood tests may be required to determine the cause of the Fever. These tests help rule out more serious illnesses and initiate a targeted therapy.

What the pet owner can do and professional therapy options

The pet owner should ensure that the cat stays in a quiet and stress-free environment. Adequate hydration is crucial, so fresh water should always be available. If there are signs of dehydration, it can be helpful to offer the cat water with a syringe if it doesn’t want to drink on its own.

The pet owner should not give the cat access to potential stressors, such as loud noises or other animals that could worsen the situation. A comfortable, warm place to sleep can help promote the cat’s well-being.

It is important never to administer medication without veterinary advice, as many human medications can be toxic to cats. Only a vet can prescribe suitable medications to relieve symptoms and treat the cause of the Fever.

Regularly checking the body temperature can help monitor the course of the illness. If the cat’s condition worsens or the Fever persists, you should see a vet immediately.

Outlook on current research

Research into Fever in cats is increasingly focusing on the molecular and cellular mechanisms that lead to an elevated body temperature. Scientists are trying to understand the role of cytokines, particularly interleukin-1 and tumor necrosis factor (TNF), which are known as endogenous pyrogens and play a central role in triggering Fever. By studying these molecules, researchers hope to find better diagnostic markers to distinguish Fever from other thermoregulatory changes.

Another area of research is the study of genetic predisposition in cats, which could lead to an increased susceptibility to Fever. Studies are analyzing genetic markers associated with an excessive immune response. The goal is to find out if certain cat breeds or lines are more prone to febrile reactions and if genetic selection is possible to reduce this susceptibility.

At the same time, intensive work is being done on the development and improvement of non-invasive methods for monitoring Fever. Researchers are testing new technologies such as infrared thermography and wearable thermal sensors designed to allow continuous and stress-free monitoring of a cat’s body temperature. These technologies could be used not only in clinical practice but also in the home environment to ensure early detection of Fever.

The role of microbiome composition in connection with the development of Fever is another emerging research area. Scientists are investigating how the balance of the intestinal flora / gut microbiota can influence immune behavior and thus body temperature. Initial results suggest that certain bacterial profiles may be associated with an increased tendency toward inflammation and thus a higher probability of Fever.

Another exciting field of research is the study of environmental factors that influence Fever in cats. This involves examining the influence of stress, diet, and lifestyle on the thermoregulation and immune response of cats. Insights from these studies could help develop preventive measures that minimize the risk of febrile episodes.

In summary, current research aims for a better understanding of the complex mechanisms behind Fever in cats. In the future, these findings could lead to improved diagnosis and therapy strategies that not only improve the cats’ quality of life but also ease their owners’ concerns.

Frequently asked questions

  1. What is fever in cats? Fever in cats is an increase in body temperature triggered by the activation of the immune response. It differs from hyperthermia, which is caused by external influences such as heat.

  2. How do I recognize fever in my cat? Signs of Fever in cats can include apathy, loss of appetite, shivering, and an increased pulse. An accurate determination is made by measuring the rectal body temperature, which is above 39.2°C in the case of Fever.

  3. Can I treat fever in my cat myself? It is not recommended to treat Fever in cats without veterinary advice. Medications for humans can be dangerous for cats. A vet can determine the cause of the Fever and initiate the correct therapy.

  4. What causes can fever have in cats? Fever can be caused by infections, Inflammatory conditions, Tumors, or autoimmune diseases. Sometimes the cause is unknown, which is referred to as fever of unknown origin.

  5. How is fever diagnosed in cats? The diagnosis of Fever involves a thorough medical history, a physical examination, and often blood tests or imaging procedures to identify the underlying cause.

  6. How long can fever last in cats? The duration of Fever varies depending on the cause. In the case of an infectious disease, it can last a few days, while chronic illnesses can lead to longer-lasting Fever that requires continuous monitoring and therapy.

  7. Can stress cause Fever in cats? Stress can affect the immune system and indirectly lead to Fever by increasing susceptibility to infections. However, a direct triggering of Fever by stress alone is rare.

  8. What role does the immune system play in Fever? The immune system plays a crucial role in the development of Fever, as the release of cytokines affects temperature regulation in the brain and increases body temperature to support the fight against pathogens.

  9. Are there preventive measures against fever in cats? Regular health checks, vaccinations, and a balanced diet can help strengthen the immune system and reduce the risk of febrile illnesses. Avoiding stress can also be a preventive measure.

  10. When should I take my cat to the vet for fever? If your cat shows signs of Fever, such as apathy, loss of appetite, or shivering, and the temperature is above 39.2°C, you should see a vet. This is particularly important if the Fever lasts longer than 24 hours or is accompanied by other symptoms.