How to Use a Rectal Thermometer

To prepare a digital thermometer, press the button to turn it on.

Hold your baby on your lap, tummy down and bottom up. Let his legs dangle over the side of your thigh. Another option: Position your baby on his back as for diaper changing, either on the bed or a changing table. He may be more comfortable in this position since he's used to having his diaper changed.

Spread apart your baby's buttocks with one hand. Use the other to grasp the thermometer between your middle and index finger, and gently insert the bulb about one inch (2 1/2 centimeters) into his rectum or until the tip of the thermometer disappears. Keep a firm grip on his buttocks by cupping them with the palm and fingers of the hand that's holding the thermometer.

A digital thermometer measures temperature within 30 seconds to two minutes and then beeps when it's ready.