As a pet owner, it is stressful when you believe your companion might be sick. A common sign of illness in both humans and pets is a fever or increased body temperature. However, unlike humans, detecting a fever in felines is not as easy as one might believe. Even though it’s a common thought, you can’t tell if your cat has a fever by feeling for a warm, dry nose. The only way to tell if your cat has a fever is to use a thermometer.

The normal temperature for a cat ranges from 100.4° and 102.5° Fahrenheit with a fever occurring at any temperature above 102.5°. Sometimes a fever can be helpful in helping your feline fight off disease or infection, but be advised that temperatures over 106° can be damaging to organs. If your cat has a high fever at or above 106°, contact your vet right away.

Causes of Fever in Cats

A general increase in body temperature is more formally referred to as hyperthermia and some cases of hyperthermia may simply be the result of your cat being in a warm environment or increased muscle activity.

However, a fever is a specific and regulated type of hyperthermia which occurs when the body’s set point is increased in the hypothalamus in the brain. Typically, a fever is the result of your cat’s immune system being activated by certain conditions such as:

• Bacterial, viral, or fungal infection
• A tumor
• Traumatic injury
• Medications
• Diseases

However, a fever that continues for two weeks or more with no apparent cause is known as a fever of unknown origin, or FUO for short.

Signs & Symptoms of Fever in Cats

Fevers are an evolutionary design to help your cat fight disease by stimulating the immune system which slows the growth of bacteria and viruses. There are certain behaviors that reveal fevers in cats were developed as a result of their wild ancestors’ need to survive. These behaviors allowed wild animals to conserve the necessary energy in order to produce a bacteria fighting fever and have been passed down to modern house cats.

Keep an eye out for these signs of fever in cats:

• Decreased or loss of appetite
• Depression
• Lack of energy or activity, general lethargy
• Decreased drinking
• Decreased grooming
• Shivering or rapid breathing

Alongside the fever, your cat may also display other signs of illness such as sneezing, vomiting, or diarrhea.  

If you suspect your cat might have a fever, you will want to take his temperature. A pediatric rectal thermometer is the most accurate method and a digital thermometer is generally safer than a glass thermometer.

In order to take your cat’s temperature, make sure you apply a lubricant to the tip of the thermometer. Then have a helper restrain the cat while you gently lift the tail and slowly insert the thermometer into the anus. You may need to gently twist the thermometer from side to side in order to relax the muscles so you can insert it about one inch into the rectum.

Be very careful not to force the thermometer as this could injure your cat. Once you hear the digital thermometer beep, you can remove it to read the result. If using another type of thermometer, understand when and how to read the results. Reward your cat with a treat if he has not been vomiting.

Treating Cat Fevers

When considering at-home care, never give your cat medication without first consulting your vet. Some medications that help with human fevers, such as acetaminophen, are toxic to cats. Or, consider a natural alternative to help your cat start feeling better. In general, let your cat rest so that he has the energy to fight off whatever is making him ill. Most cases of fever in cats will resolve naturally within a day, but that is not always the case.

If your cat has had a fever longer than 24 hours or it is greater than or equal to 106°, take him to the vet immediately. Your veterinarian may conduct tests to diagnose and treat the underlying cause of the fever. If there is a bacterial infection, antibiotics may be administered. If your vet does prescribe medication, be sure to explicitly follow the directions given by your veterinarian, finishing the full course of medication even after the symptoms have abated. Dehydration, which may occur as the result of a fever, could be treated with intravenous fluids by your vet.