Getting started

Unfortunately, babies sometimes get sick, and a fundamental clue that things are amiss is a fever—a body temperature that's higher than normal. Most pediatricians consider any thermometer reading of 100.4 degrees F or higher a sign of fever. A fever can be alarming, but except in the case of heat stroke (a dangerous rise in body temperature caused by a sweltering environment, like a car with the windows rolled up in August), a fever by itself isn't an illness. It's the immune system's way of signaling that it's working to fight an infection.

Still, fever is often the first sign of illness, and your baby's temperature reading—coupled with your baby's other symptoms (if any)—will help your pediatrician to diagnose the cause of a fever. But accuracy is imperative. For babies under 3 months old especially, every 10th of a degree counts. The difference between a temperature of 100.3 degrees F and 100.4 degrees F, for example, can determine whether you stay home or take your baby to the emergency room. Any fever in this age group is typically considered an emergency. If your baby is under 4 weeks old, and has a fever of 100.4 degrees F or greater, call your pediatrician immediately. A baby that young with a fever of 100.4 degrees F or higher will most likely need to be hospitalized to rule out serious infection. For babies 4 weeks to 3 months old, it's still an emergency that needs prompt medical attention.

Read more:

thermometers/thermometer-buying-advice/thermometer-guide/what-to-do-when-your-baby-has-a-fever/thermometers-what-to-do-when-your-baby-has-a-fever.htm?EXTKEY=AMYC0BK">What to do if your baby has a fever

For your baby's first thermometer, go with an inexpensive digital model. Look for an LCD display that's easy to read and a start button that's easy to press. But don't be swayed by digital thermometers that claim to take a reading in an instant. A reading in 20 to 60 seconds is quick enough.

Types

Due to the toxic risks of mercury, digital thermometers have replaced the glass thermometers you may have grown up with. In fact, if you have a mercury thermometer, get rid of it, advises the American Academy of Pediatrics (AAP). But don't just throw it away. Your doctor or local health department can tell you how to dispose of it properly. Here are the types of thermometers to consider.

Digital thermometers are easy to read and they don't expose your baby to the mercury in a glass thermometer, which is dangerous if the thermometer breaks. Get a digital thermometer that can be used rectally. You can also take a baby's temperature by mouth, by ear, on the forehead, or under the arm, but the AAP considers rectal readings to be the most precise way to take a temperature in infants and children younger than 3. (We've found in our tests that forehead models are especially imprecise.) After your baby's first birthday, your pediatrician might allow you to use a different temperature-taking method, so be sure to ask what's acceptable at that point, if you want to switch.

A popular option you'll see in stores and online is digital ear (tympanic) thermometers, which measure body temperature inside the ear. "They aren't recommended for young children because there are lots of chances for error," Paul Horowitz, M.D., a founding pediatrician at Discovery Pediatrics in Valencia, Calif., said. We've found that you have to align them in the ear canal perfectly for them to be accurate.

Temps taken orally, with a pacifier thermometer (a digital oral thermometer that looks like a pacifier; it displays a reading after your baby sucks on the pacifier for 90 seconds), might seem to be another way to go. But oral thermometers tend to be as much as 1 degree F lower than rectal thermometers and aren't considered as accurate for children under 3.

Features

As simple as digital thermometers are, some have bells and whistles that you might find convenient—beeps that tell you when they're in the right spot or when they're finished, or soft or curved tips. Here are the baby thermometer features to consider.

When you're trying to take a wiggly baby's temperature, you don't have much time to get the job done. Some thermometers claim to display a reading in as fast as five seconds, but in our opinion, a reading in 20 to 60 seconds is fine.

To take the guesswork out of insertion, some rectal thermometers feature an indicator or design that makes it easy to know if the thermometer is positioned properly—a definite plus.

Life with an under-the-weather baby is unpredictable. You'll want a digital thermometer that can withstand dropping, being submerged in water, even being gnawed on by your little one.

Some thermometers "remember" the last temperature read. That can be useful, especially in the middle of the night when you're sleep-deprived and trying to determine in which direction your baby's fever is going. Some also feature an automatic shutoff to preserve battery life. That's a plus, too.