A review was carried out on the effectiveness of different types of thermometers. Out of all, a rectal thermometer is the best. Also, methods like measuring body heat on forehead or under the arms are not precise enough.

Head of the review, Dr. Daniel Niven, an intensive care physician with the Peter Lougheed Center in Calgary, said that the finding does not means that one has to have a rectal thermometer with them. As per him, the oral thermometer and ear thermometer are also accurate options.

In the research, Niven and colleagues have assessed data from 75 different studies carried out across the world in which more than 8,600 patients were included both adults and children. The researchers studied the measurements taken from the armpit, mouth, ear and forehead, known as peripheral thermometers.

They also compared measurements with more invasive thermometers called central thermometers that are placed inside the rectum or inside the bladder. Niven said that the more invasive measures were of gold standard.

The research is important as if a temperature is found to be normal when it is not then it can lead to serious infection that may go unnoticed. Niven hopes that the study findings will encourage doctors to go for central thermometers.

Though 98.6 degrees is considered as normal temperature, between 97 and 99 is also considered to be in normal range of body temperature.