Ever notice that a cat is particularly nice to cuddle up to on a chilly night? That's because the average body temperature for a cat is 101.4 degrees Fahrenheit -- about 38.6 degrees Celsius -- (a good three degrees warmer than ours). An individual cat's temperature may range between 100 and 102.5 degrees Fahrenheit and still be considered "normal." Disease -- or prolonged exposure to heat or cold -- can send a cat's temperature above or below the normal range.
Usually, a mild fever is a normal part of a cat's natural disease-fighting system. But extremely high or persistent fever can do serious -- or even fatal -- damage, and calls for professional help. You can't really rely on touching your cat to tell if he's running a fever, and you can't get him to hold a thermometer under his tongue. Unfortunately, the most accurate and reliable way to take your cat's temperature is the way he's going to like least -- rectally. Of course, your cat isn't going to like this, especially if he or she is already not feeling well. If your cat is already showing signs of being ill, it may be worth trying. If you can manage to take your cat's temperature, it can help to let the vet know that he or she is running a fever before you get to the office.
Obviously, a rectal thermometer is the equipment called for here; you'll want to have a dedicated "cat thermometer" on hand ahead of time. A digital one is best. Lubricate the end with petroleum jelly or vegetable oil. With your cat's feet firmly planted on a secure surface, tuck him or her under one arm with the tail pointed outward and the nose back by your elbow. (This may be a two-person operation.) With the hand of that same arm, hold the cat's tail up, and gently insert the thermometer in the anus with the other hand (you may have to bear down slightly at first). Slowly insert the thermometer about one inch, and keep it there for up to three minutes, if possible. Gently remove the thermometer, wipe it off, and read the temperature. Write it down so you can report it accurately to the vet when you call.
Now you know how to examine your cat inside and out, and hopefully, we've given you a better idea of when it's necessary to take him or her to the vet. If you do decide it's time for a visit, you can tell your vet exactly what you've observed, and your cat will be soon be on the road to recovery.