Modern digital thermometers are faster than mercury thermometers, don't have to be shaken down, and are much safer if bit, dropped, or stepped on.
The most accurate temperature measurement in infants and young children is a rectal reading. In school-aged children, an oral measurement is ok to use.
Axillary (armpit) temperatures are ok to use to screen your child's temperature, but remember they are inaccurate 33% of the time. If an axillary temperature suggests your child has a fever, get a more accurate reading by using an oral or rectal temperature.
Some of the new ear thermometers work well if used correctly, but this takes a lot of practice. We don't recommend using the forehead strip and commercial-grade forehead "wand" thermometers. They are not really accurate at all.
Regardless of which method you use, please don't add or subtract degrees to the measurement. Recent evidence demonstrates that doing so, even though it is common practice, confuses the picture. Report to us the actual thermometer reading.
How to take a rectal temperature
Hold the baby on his or her stomach across your lap. Let his or her legs hang down freely. Gently insert the thermometer about 1/2" into the baby's rectum. Hold the thermometer between two fingers as you lay the palm of your hand across the baby's buttocks. Don't leave the baby alone with the thermometer inserted. Leave the thermometer in until the reading has finished. Be sure to clean the thermometer well with soap and warm water after use.
How to take an oral temperature
Have your child sit or lay down as long as thermometer is in his mouth. Gently insert the thermometer under your child's tongue as far as it will comfortably go. Hold it in place (or have your child hold it) until the reading is finished. Don't let your child talk or breathe through his mouth. Be sure the thermometer stays under the tongue by watching the angle of the thermometer. A correctly-placed thermometer should point up. A thermometer that has slipped out of place will be level or point down.
How to take an ear (otic) temperature
Follow instructions that come with the thermometer. Remember that, to get an accurate reading, there must be a good seal around the tip of the thermometer, and the tip must be aimed straight toward the eardrum.
How to take an axillary (armpit) temperature
Have your child sit or lie down. Place the tip of the thermometer into the middle of the armpit, against the child's bare skin. (Don't do it through your child's t-shirt or nightgown.) Hold the thermometer in place with one hand. Keep your child's arm pressed firmly against his side with your other hand until the reading is taken.