Fever is an elevated body temperature that occurs as a response to infection or inflammation (also see hyperthermia). It is a common misperception that fever always indicates infection – this is not the case. It may be due to autoimmune diseases, heat stroke, or cancer as well.Normal body temperature is 101 to 102.5°F for both dogs and cats. The temperature is most accurately taken with a rectal digital electronic thermometer; these usually give results in less than one minute. Lubricate the thermometer with a water-based lubricant (such as K-Y jelly, baby oil or soap), and then insert the thermometer about 1-2 cm (about 1/2 to 1 inch).

Ear thermometers designed for humans do not work well in pets. 

What to Do

• Take and record the rectal temperature if you pet feels ill or warm. If it is above 103°F, call your veterinarian or local emergency center. A temperature above 106°F can be life threatening and demands immediate attention. 
• If the animal's temperature is over 105.5°F, moisten the pet's hair coat with cold water and pay particular attention to the ears and feet, which are sites of heat exchange. Direct a fan on the moistened areas. 
• Encourage (but do not force) your pet to drink small, frequent quantities of water unless she has vomited in the past 4 to 6 hours.

What NOT to Do

• Be careful not to overtreat! Discontinue cooling once the rectal temperature reaches 103°F or the pet may become too cold (hypothermic). 
• Do not give aspirin, ibuprofen, acetaminophen or other drugs as many of these are poisonous to pets.
• Do not demand antibiotics from your veterinarian for all causes of fever.

When a pet is lethargic, depressed, shivering a lot, or you see any other reason to suspect that she is not well (not eating, or is vomiting, coughing, has greenish nasal discharge), suspect a fever. The only way to confirm this is to take her temperature using a medical thermometer. Detailed information on taking rectal temperature can be found in the in the temperature section of the Physical Exam Checklist.