Temperature readings vary from one healthy person to another and are influenced by factors such as age, gender, and ambient temperature. Temperature readings vary even in the same person at different times. Therefore, normal body temperatures can only be given as ranges.
Readings from different parts of the body also differ from each other. For example, rectal temperatures tend to be higher than oral (mouth) temperatures, and ear and armpit temperatures tend to be lower than oral temperatures. Here are ranges of average temperatures of healthy people taken from different body sites in various studies (Sund-Levander et al 2004):
Mouth 33.2°C to 38.2°C
Armpit 35.5°C to 37.0°C
Because of the wide variation in “normal” temperatures, Age Smart instructions suggest that you find out your normal temperature ranges by taking your temperature several times when you are feeling healthy. Guidelines issued by NICE (National Institute for Health and Clinical Excellence) suggest that fever should be defined as “an elevation of body temperature above the normal daily variation” (NICE 2007).
National Institute for Health and Clinical Excellence (NICE). National Collaborating Centre for Women’s and Children’s Health. Feverish illness in children. Ed. Welsh A. RCOG Press at the Royal College of Obstetricians and Gynaecologists. 2007. http://guidance.nice.org.uk/CG160
Sund-Levander M, Grodzinsky E, Loyd D, Wahren LK. Errors in body temperature assessment related to individual variation, measuring technique and equipment. Int J Nurs Pract. 2004;10(5):216-23.