What Does Your Fever Mean?

January 3, 2018

Mark L. Friedman, MD, FACEP, FACP

Fevers are certainly draining and unpleasant. Fevers aren’t an illness--rather they’re a symptom of the body’s response to illness. When the body is invaded by viruses, bacteria or other infection the immune system turns up your internal thermometer in an attempt to create an environment that is unwelcoming to the intruders.  


The patient’s temperature is an important parameter (measurement) to provide to your doctor. Keep a good digital thermometer at home and with you when you travel. Core temperatures (rectal) are the most accurate. Second best are oral. After that ear thermometers are OK. The ones that measure temperature of your forehead or axilla (armpit) are misleading and therefore worthless.

What Causes Fevers?

A fever occurs when the body's core temperature is increased above the normal range (97-99 degrees). 

  • Infectious fevers are the most common and the result of the hypothalamus cranking up the body's internal temperature to fight infection. These fevers can be the result of less serious conditions such as colds, or more serious conditions, such as influenza and meningitis.  
  • Inflammatory fevers can last for weeks. These can be associated with autoimmune diseases and cancers such as leukemia and lymphoma. 

Other recognized, but less common, causes of fever are severe sunburn, heat exhaustion, broken bones, and other conditions like rheumatoid arthritis. Rarely, medications and even immunizations (diphtheria and tetanus) can cause fevers. 

The main question is, “What is causing the fever and how should it be treated?”

Persistent fevers (more than 3 days) and any fever above 102.5f without an obvious source should be investigated to determine the cause.

Originally published Jan 3, 2018 1:00:00 PM.