For starters, you'll need a good digital thermometer, which you can find in drugstores/pharmacies. Digital thermometers are easy to use, easy to read, and fast – most give an accurate reading in ten seconds to two minutes.
Some digital thermometers are specifically designed for use in the rectum, but most can be used rectally, orally, or under the arm. (If you take your baby's temperature using more than one method, you'll want to designate a thermometer for each.) Digital ear thermometers, called tympanic thermometers, are usually more expensive and can only be used in the ear.
That leads to the question of where to put the thermometer to get the best reading: in the rectum, the ear, or the armpit. (Taking your child's temperature orally won't be an option until he or she is older.) Each method has advantages and disadvantages, so talk it over with your doctor to see which method he or she recommends for your baby.
Regardless of the method you use, don't take your baby's temperature right after he or she has had a bath, as it could affect your baby's body temperature. Wait at least 20 minutes after bath time for an accurate reading.
Your doctor may ask you to take a rectal reading because it consistently gives the most accurate results. Most of the research that your baby's doctor relies on to decide how to respond to a fever is based on rectal temperatures.
Some babies don't mind having their temperature taken rectally, while others just seem miserable being subjected to this procedure. If your baby protests, you might want to take an underarm (axillary) temperature first and then take a rectal temperature if the first reading is over 99 degrees Fahrenheit.
Ensure your doctor teaches you how to use the rectal thermometer before you try it.
Ear thermometers are generally used in urgent care centers because they're quick, safe, and not at all uncomfortable. The only problem is that they're a little trickier to use than other digital thermometers. In fact, if you don't insert the ear thermometer exactly right, it can be hard to get an accurate, consistent reading.
If this method appeals to you, you might ask your baby's doctor to show you how to use an ear thermometer or practice following the directions on the package until you get a consistent result. While you're getting the hang of it, you may want to confirm your results with a rectal reading. Once you consistently hit the mark, you can rely on the ear thermometer.
Ear thermometers aren't recommended for babies younger than 3 months because little babies' narrow ear canals make it hard to insert the sensor properly.
Under the arm
Some doctors recommend taking a baby's temperature in the armpit, which is called the axillary temperature. It's easy, convenient, and safe, and all you need is a regular digital thermometer.
The downside is that an armpit reading is far less accurate than other methods. In fact, an external armpit reading can be as much as 2 degrees lower than an internal rectal reading. It's advised that you don't use this method for babies under 3 months of age, when an accurate reading is most important.
For an armpit reading, undress your baby from the waist up and cradle him or her. Try to keep your baby relaxed – you may want to feed your baby or offer a toy.
Make sure your baby's underarm area is dry, then slip the bulb of the thermometer into the armpit. The bulb needs to be in full contact with your baby's skin, so hold your baby's arm firmly against his or her side or bent and folded across the chest. When the thermometer beeps, take it out and read the display.
Other methods you can use:
Hold off on using an oral thermometer until your child is at least 4 or 5 years old. It's virtually impossible to get an oral reading from a baby or toddler.
If your baby uses a pacifier, you might be able to get a decent reading with a pacifier thermometer. These are recommended for children between 3 months and 2 years of age, and they require that your baby keep the pacifier portion in his or her mouth for about three minutes. Pacifier thermometers yield results that are a bit low, so if you use one, add half a degree Fahrenheit to the reading you get.
No other methods are currently considered reliable. The temperature-sensitive strips that you place on a child's forehead may be convenient for a quick temperature read in a pinch, but don't use one when you need an accurate reading.
Using your skin or palm to feel your baby's temperature cannot give you accurate result also. It can only show you your baby's body is hot, warm or cold. Always make sure you use thermometers to check your baby & of cos stay kamsified!