How Does a Rectal Thermometer Work?

Types of Rectal Thermometer

There are many types of rectal thermometers, though they all function similarly--and, of course, they all have the same purpose. Some thermometers have flexible tips while others have rigid tips. Some are shaped for a better grip, others are skinny for better space management. Almost all rectal thermometers these days are digital.

Process

The rectal thermometer must be inserted into the rectum. This can obviously be uncomfortable (even painful for some), not to mention awkward. Nonetheless, the rectum should be prepared by having some sort of lubricant (preferably water-based) rubbed lightly onto it. The thermometer should be positioned against the rectal hole and slowly pushed inside. The tip of the thermometer need only penetrate an inch or so to take an accurate temperature reading, and usually must be held for at least 20 seconds.

Why the Rectum?

Though people typically prefer having their temperature taken via the mouth or the armpit, the truth is that the rectum is the most accurate place in which to take a temperature reading. This creates an awkward situation for some, of course; this is why the rectum as a source for temperature data is usually reserved for young infants. Older people, especially adults, almost always prefer another area, and doctors are almost always willing to oblige.