What is a Normal Body Temperature?

What is a normal temperature? I have flu symptoms and a temp of 97.2 to 99.8. Can that still be the flu? I take Verapamil, Ziac, Synthroid, and tamoxifen. I had a left breast lumpectomy six months ago and 28 treatments of radiation. Would my medicines affect my temperature and cause me to have a low fever with the flu?


For such a simple-sounding question, there is no simple answer. Most people think of 98.6 degrees Fahrenheit (37 degrees Celsius) is a normal body temperature. This is clearly not an adequate answer. A person's temperature depends on a lot of different factors, not the least of which is the way the temperature is measured. Rectal temperatures tend to be a little higher than oral ones. Tympanic-membrane (ear) temperatures can be accurate, but if done incorrectly they are highly variable. A person's normal temperature also varies throughout the day, with the lowest temperature being in the morning and the highest in the late afternoon and early evening. Most studies of temperatures in normal people have shown that normal body temperature is rarely above 99.9 degrees Fahrenheit (37.7 degrees Celsius), even in the evening.

Fever is frequently defined as the elevation of body temperature in response to an infection or other disease process. Using the upper limit of normal as 99.9 degrees Fahrenheit, fever would be defined as 100 degrees Fahrenheit (37.7 degrees Celsius) or higher. This is the definition I typically use. Some physicians define fever as 100.4 or 101 degrees Fahrenheit (38 or 38.3 Celsius), however, and I do not believe there is just one correct answer. One important note is that the height of the fever does not necessarily relate to how severe the infection is. One of the danger signs in patients who develop pneumonia is hypothermia, or low body temperature. If temperature is low, a pneumonia patient is less likely to survive.

Certain infections, such as malaria, typically give a high fever. Other infections, such as the common cold, would be unlikely to give fever much higher than 100 degrees Fahrenheit. Patients with influenza typically have fever, which can be as high as 104 or even higher, though some patients with confirmed influenza do not have a high fever. Fever alone is not enough to make an accurate clinical diagnosis. The other classic findings of influenza are the sudden onset of symptoms, headache, severe body aches and cough. If you had none of these symptoms, and a temperature that never rose above 100, I would doubt that you had true influenza.

Some medications can alter the body's normal fever response. The most important are acetaminophen (trade name Tylenol) and the anti-inflammatory drugs such as ibuprofen (Advil) and naproxen (Aleve). These drugs are given to relieve fever, and they usually work. However, in my experience, if patients have true infections, they will still develop some fever, even if on these drugs. On the other hand, corticosteroids such as prednisone (Deltasone) may prevent fever from occurring entirely. This does not happen in all cases, but if someone is on one of these drugs and infection is suspected, the lack of fever should by no means rule out the diagnosis of infection. I am not aware that any of the medications you are taking can prevent fever.

One side note is that women who have had breast cancer, radiation and lymph nodes removed are at particular risk of skin infection of the arm on the side of the surgery. If the lymph nodes are removed and swelling occurs, the patient is at risk of significant streptococcal infection on that limb. Sometimes the patient may have fever and body aches before there is any sign of infection on the arm.

by Harold Oster