The temperature inside the human body is normally between 36 and 37 degrees Celsius. A value between 37.5 and 38 degrees Celsius is called elevated temperature. If the temperature is higher than 38 degrees Celsius, then in adults it is called a fever. If the temperature rises above 39 to 41 degrees Celsius, the affected person has a high fever. Extremely high fever is present when a body temperature of over 41 degrees Celsius is measured. All these indications apply to rectal measurement.
Fever is not a disease of its own, but a symptom. It can occur with a whole range of different diseases. The most common cause is acute infectious diseases, which also include colds and flu.
A fever is an increase in body temperature beyond the naturally set “target” temperature. Fever is a symptom, not an independent disease. It can occur with a whole range of different clinical pictures. Since the body temperature also fluctuates in healthy people (see below), one speaks of fever only above certain limit values: measured orally (i.e. in the mouth), fever means an increase in body temperature to over 37.8 degrees Celsius (° C), measured rectally (i.e. in the anus) only from 38.2 ° C.
The body temperature is usually around 37 ° C, which means the core body temperature, i.e. the temperature inside. Certain areas of the body, such as the chest or the brain, are warmer than other regions of the body. In the thighs and upper arms, the temperature is only between 34 and 36 ° C, in the feet and hands it is even cooler with an average of 28 ° C. Therefore, when measuring body temperature, it is always important to name the place of measurement. The axillary measurement (i.e. in the armpit) is very unreliable. If the body temperature deviates very much from the normal value, this can lead to tissue and organ damage. Thus, a temperature of more than 42.6 °C is usually fatal.
The body temperature depends on various factors and is therefore never completely constant. Thus, the temperature fluctuates over the course of a day: in the morning, on average, 36.2 ° C is measured orally (36.0 °C axillary and 36.5 °C rectal). Over the course of a day, the temperature rises by up to 1 °C to about 37.5 °C orally. (37.2°C axillary, 37.8°C rectal). Physical activity can warm the body by about 2 °C. Even an opulent meal can “heat up” the body. In women, the body temperature rises by about 0.5°C in the 2nd half of the cycle, that is, after ovulation until the next menstrual period. However, normally the body temperature does not rise above 37.8 °C.
What is considered a fever?
Is a fever 99 or 100?
Is a fever of 100?
Is 99.6 a fever for Covid?