Temperature takingTell the doctor which thermometer you used, the body part you took the temperature from, and the exact reading you got. When choosing a thermometer, factor in your baby's age. (Mercury has been linked to nervous-system damage, so if you have a mercury thermometer, bring it to your pediatrician for disposal.) Here are the options:
Rectal For babies under 3 months, when even a slight fever can be serious, you'll want a rectal thermometer, which is the most accurate. Lubricate the tip with petroleum jelly. Place your baby on his back, lift his legs like you're changing his diaper, and slide the thermometer about a half inch into the rectum. The Safety 1st 8-Second Fold-Up Thermometer ($10, babiesrus.com) speeds up what can be an unpleasant task.
Temporal artery This new type of thermometer, used by many hospitals, is suitable for all ages. Just place it in the center of the forehead and sweep over to the hairline; a reading takes one second. Try Exergen's Temporal Thermometer ($30, walmart.com).
Underarm Armpit readings are fine for babies over 3 months, though they'll usually register a degree low. Place the thermometer tip in the center of your child's armpit and press his arm firmly against his chest. Hospital's Choice 10-Second Digital Thermometer gives underarm, rectal, or oral readings ($10, amazon.com).
Pacifier Binky thermometers can be a lifesaver, though on average they're half a degree low. Just place it in the baby's mouth. Lumiscope's Babytherm ($18, amazon.com) beeps when the reading is complete.
Ear This convenient method isn't ideal for babies under 12 months, as it can give a false high or low reading. Gently pull the upper part of your child's ear back and up. Place the probe straight into the ear canal. Then take several readings to determine if your baby has a fever. The Summer Infant Digital Ear Thermometer ($25, diapers.com) takes readings in one second.