- Like other sorts of thermometers, rectal thermometers come in two main types. They can be mercury thermometers, meaning they have mercury inside that rises alongside a measurement scale and must be manually read to indicate body temperature, or they can be digital thermometer, displaying the reading in numbers on a small screen. A digital thermometer often gives a beep when it is time to read the temperature.
- A rectal thermometer is usually covered with a plastic shell and then inserted with lubricant into the rectum. Depending on the type of thermometer, it will need to stay in place for one to three minutes to get an accurate reading. It is helpful if the patient sits still while checking the rectal temperature.
- Rectal thermometers usually come in a standard size; they are neither bigger nor smaller than a standard oral thermometer. As such, they are usually about three inches long and perhaps a quarter of an inch wide at the point that is used for insertion.
- Rectal temperatures are thought to be the most accurate readings, because they are taken in an area of the body where there will not be much fluctuation in temperature. In the mouth, for example, readings may be inaccurate because a person's oral temperature might vary based on whether the person has had her mouth open recently or whether the person has had something hot or cold to drink recently--or even if the person's tongue wiggles around while checking the temperature. In addition, rectal thermometers can be beneficial for those who cannot or will not cooperate with the oral temperature taking process, such as very small children or your pet.
- Whenever using a rectal thermometer, use a plastic slip cover for sanitation reasons and make sure that the rectal thermometer is reserved for only rectal use (it should not alternate between being a rectal and an oral thermometer). In addition, it is a good idea to use lubricant to prevent unnecessary discomfort and to avoid inserting the thermometer too far into the person's rectum--especially when using a rectal thermometer on a newborn baby, who may be prone to having tissue tears.
