Fever in Cats: Signs, Normal Temperature and What to Do

By Tailwisp Editorial TeamUpdated October 20, 20264 min read

A warm nose does not mean a fever, and a cool nose does not mean health. Cats hide illness, so a fever can go unnoticed until the cat is quite sick. Knowing the normal range, how to measure, and what to do can make a real difference.

What is a fever?

A fever is a rise in body temperature, set by the brain in response to infection, inflammation or other triggers. It helps the immune system fight invaders, but too high or too long can harm the cat. Do not confuse it with hyperthermia, which occurs when the body overheats from outside heat, such as in heatstroke. See heatstroke in cats.

Normal and abnormal temperatures

• Normal: about 100.5 to 102.5°F (38 to 39.2°C).
• Mild fever: about 103 to 104°F (39.4 to 40°C).
• High fever: above 104°F (40°C), and see a vet promptly.
• Dangerous: above 106°F (41.1°C).
• Low (hypothermia): below about 99°F (37.2°C), also an emergency.

Signs

• Lethargy, and hiding.
• Reduced appetite, or refusing food.
• Shivering, or seeking warmth.
• Rapid heartbeat and breathing.
• Dehydration.
• Reduced grooming.
• Vomiting or diarrhea, depending on the cause.
• Sometimes none at all.

Feeling ears, nose or paws does not tell you the temperature.

How to take a cat's temperature

A digital rectal thermometer is the most accurate way, and the vet will usually do this. If your vet advises you to do it at home:

1. Use a pet or digital thermometer, with a flexible tip, and lubricate it with petroleum jelly.
2. Have a helper hold the cat, gently, standing or on its side, or wrap in a towel.
3. Lift the tail, and insert the thermometer about an inch, gently, aiming slightly toward the belly.
4. Hold until it beeps.
5. Wipe, clean and reward your cat.

Ear thermometers made for pets can be less accurate. Stop if the cat struggles. See how to check your cat's vital signs.

Causes

• Infection, bacterial, viral or fungal. See feline calicivirus and herpesvirus and cat bite wounds and abscesses.
• Urinary or kidney infection. See urinary tract infection in cats.
• Dental abscess. See cat dental disease.
• Pyometra. See pyometra in cats.
• FIP. See feline infectious peritonitis.
• Immune-mediated disease, and inflammation, such as pancreatitis. See pancreatitis in cats.
• Cancer. See cancer in cats.
• Reaction to vaccines or drugs.
• Fever of unknown origin, where no cause is found at first.

What not to do

Do not give acetaminophen (Tylenol), ibuprofen, naproxen or aspirin, which are toxic to cats, and can be fatal. Do not give any human medicine. Do not wrap a feverish cat in heavy blankets, or use cold baths. See cat poisoning: what to do.

What to do

• Take the temperature, if instructed.
• Keep your cat comfortable, in a quiet room.
• Offer water, but do not force it.
• Call your vet, and describe other signs.
• Go to the vet the same day for a temperature of 103°F or more with illness, immediately for 104°F or more, or for low temperature.

Diagnosis and treatment

The vet will examine your cat, and may run bloodwork, urine tests, X-rays or ultrasound. Treatment depends on the cause: antibiotics, antivirals, fluids, anti-inflammatory drugs safe for cats, treatment of abscesses, surgery and nutritional support. See cat blood tests explained.

Kittens and seniors

Kittens and seniors can become very ill with fever, quickly. Seek care promptly. See kitten first vet visit.

Fever of unknown origin

Sometimes a fever persists and tests do not reveal a clear cause. Vets call this fever of unknown origin, and the workup may include repeated bloodwork, imaging, tests for infectious diseases and cultures. Some cats improve with antibiotics and supportive care, while others need more advanced tests, such as a bone marrow sample or a referral to an internal medicine specialist. Keep a temperature log if your vet agrees, along with notes on appetite and energy.

After a fever resolves

Once a cat recovers, ease back into normal routines. Offer small meals, plenty of water and quiet rest. Watch for a relapse over the next week. If the cause was a bite abscess, keep the cat indoors until fully healed. If vaccination was the trigger, note it for your vet's records. Return for any recommended recheck.

Hypothermia

A low temperature, below about 99°F, is also dangerous. It can follow shock, severe illness, kittens being separated from their mother or exposure to cold. Wrap the cat in a warm, dry towel, put a warm water bottle wrapped in cloth nearby, and go to the vet at once. Do not use hot water bottles directly or heating pads on high, which can burn.

When to see a vet

See a vet the same day if your cat seems unwell and has a fever. Use the US vet directory to find a clinic.

This article is general educational information, not veterinary advice. Every cat is different. If your cat is unwell, or you are unsure about a symptom, diet change or medication, contact your veterinarian.