Your cat hasn't been his usual whirlwind of energy, dashing across the room to chase his favorite toys. The rattle of his food bag fails to bring him running to his dish. If your cat is acting sick, you might want to check to see if he's running a temperature. The most accurate way to gauge a cat's temperature is by using a rectal thermometer. Ear thermometers designed specifically for cats can also give a fairly accurate temperature reading. But if you don't have one of these or don't think your cat will stand for you to take his temperature, there are other ways to tell if he has a fever.
A healthy cat's temperature should be 100.4-to-102.5-degrees Fahrenheit. If it's higher than that, it's likely he's running a temperature and is ill. Signs of running a fever include lethargy, loss of appetite, decreased grooming, and shivering. Like humans, cats get a temperature when their immune system kicks in to fight a disease or pathogen.
Your cat might have an infection caused by bacteria, a virus, or fungus. Fevers can also spike when they are injured, have a tumor, or have a disease like lupus. Without a thermometer, it will be difficult to tell just how high a fever is, but a visit to the vet is in order if you see other signs of fever, if your cat is sick for more than a couple days or refuses to eat or drink.
Check the nose
Cats' noses are usually cool and moist, which you may notice when your cat nudges you with her nose to get up and play or feed her at 3 a.m. But sick cats' noses are often dry and warm when they have a fever. However, sometimes their noses are dry if they are dehydrated. Try gently lifting some fur and skin on your cat's back. If it doesn't snap back into place quickly, she may be dehydrated rather than feverish.
When your cat is well, place a finger on the inner side of her ear. It will feel warm. But when she has a fever, it will feel noticeably hotter, similar to when you feel a person's forehead to see if it's hot when fever is suspected.
Like his ears, your cat's back may also feel warmer than usual to the touch if a fever is present. But first, make sure your cat hasn't been napping in his favorite sunny spot or in front of a furnace vent.
Fast breathing and shivering
Sometimes cats who spike a fever start to breathe more quickly or pant. As in humans, shivering might also be a sign of fever.
What to expect at the vet
If you spot these signs and your cat is not acting well, it is time to go to the vet for a thorough evaluation and accurate temperature reading. Your vet will go over your cat's medical history, including contact with ill animals, allergies, vaccinations, and recent illnesses. The vet will likely order a complete blood count and biochemistry panel, as well as a urinalysis. If the cause of the illness isn't clear, scans such as ultrasound, MRI, or CT, may be performed to get a better look at what's going on internally.
The most common treatment for fever is antibiotics, often in combination with IV fluids. Sometimes an injection of a long-lasting antibiotic is given, or antibiotic pills must be given to your cat once or twice a day. But if the cause is not an infectious agent, such as a tumor or auto-immune disease, that underlying cause of the fever will be addressed.