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Temperature Taking

Children often feel warm to the touch when they have a fever, but putting your hand to your child's forehead is not enough to find out if your child has a fever. To confirm that your child has a fever, use a thermometer to measure your child's body temperature. There are several ways to do this.

Thermometer types

The easiest way to measure your child’s temperature is with a digital thermometer. These are available at most drug stores. There are other types of thermometers, including the mercury-in-glass type, ear (tympanic) thermometers, and pacifier type thermometers.

Most glass thermometers contain mercury, which is toxic. DO NOT USE A GLASS THERMOMETER WHICH CONTAINS MERCURY.

If you only have access to a glass thermometer, take very special care. If the thermometer is cracked or damaged in any way, do not use it. Even an undamaged glass thermometer can be a risk for your child. If you believe your child may bite down on the thermometer, do not use it to take a temperature in the mouth.

Four places to take a child’s temperature

  • in the mouth
  • in the rectum
  • under the armpit
  • in the ear

Do not use a rectal thermometer in the mouth or an oral thermometer in the rectum. Always wash any thermometer with soap and warm water before and after use.

The best way to take a temperature depends on your child’s age

Details of the different ways to take a temperature are described below.

Newborns to 2 years

The most accurate way to take a baby’s temperature is with a thermometer inserted into the anus (rectal temperature). If this is not possible, use the armpit method.

Children aged 2 to 5

For toddlers aged 2 to 5, a rectal temperature is the most accurate but may be difficult. Ear temperature or armpit method can also be used.

Children over 5 years of age

For children over 5, take a temperature by the mouth (oral method). Ear temperature or armpit method can also be used.

Taking a mouth (oral) temperature

Taking a temperature in the mouth works with children who are old enough to hold the thermometer under their tongue and who will not bite the thermometer. Make sure your child has not had a cold or hot drink in the 30 minutes before taking their temperature.

Oral Temperature
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  • To get an accurate reading, carefully place the tip of the thermometer under your child’s tongue. 
  • Ask your child to keep the thermometer in place by forming a seal with his lips. Make sure he doesn’t bite down on the thermometer. If he cannot breathe through his nose, use one of the other methods described on this page.
  • If you are using a glass thermometer, leave it in his mouth for about three minutes. If you are using a digital thermometer, leave it in his mouth until you hear it beep.
  • Carefully read the temperature on the thermometer. 
  • Turn off the thermometer, wash the tip with soap and warm (not hot) water, and wipe it off with alcohol. Dry well.
  • Fever is an oral temperature of 37.8°C (100°F) or more.

Taking a rectal (in the bottom) temperature

Using the rectal method works best on babies and young children. Older children may resist having something put in their bum.

Rectal temperature
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  • If using a glass thermometer, hold the top and shake until the line goes below 37.2°C (99°F).
  • Before taking your child’s temperature, make sure he is relaxed. Place your child on his stomach on a comfortable surface like a bed or a couch.
  • Before inserting the thermometer, make sure it is clean. Coat the end of it with petroleum jelly (Vaseline). This will make it easier for insertion.
  • Insert the thermometer gently into your child’s rectum about 2 cm (1 inch). If there is any resistance, pull the thermometer back a little. Never try to force the thermometer past any resistance. This could damage the wall of the bowel.
  • Hold your child still while the thermometer is in.
  • Leave a glass thermometer in your child's rectum for 2 minutes before you take it out. If you are using a digital thermometer, take it out when you hear the signal (usually a beep or a series of beeps).
  • Read the temperature. If you are using a glass thermometer, you may have to turn the thermometer until you can see the end of the line.
  • Turn off the thermometer, wash the tip with soap and warm (not hot) water. Dry well.
  • Fever is a rectal temperature over 38.0°C (100.4°F).

Armpit (axial) temperature

To take a temperature in the armpit, your child must be able to hold his or her arm to the body and not move it for about 4 or 5 minutes.

Armpit Temperature
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  • If using a glass thermometer, hold the top and shake until the line goes below 37.2°C (99°F). If you are using a digital thermometer, turn it on.
  • Put thermometer under your child’s dry armpit. The silver tip must touch the skin.
  • Hold the top of thermometer with one hand and hold down your child’s arm with the other hand.
  • If using a glass thermometer, wait 4 or 5 minutes before removing. If using a digital thermometer, wait until you hear the signal (usually a beep or a series of beeps).
  • Turn off the thermometer, wash the tip with soap and warm (not hot) water. Dry well.
  • Fever is an armpit temperature of 37.2°C (99°F) or more.

Ear method using a tympanic thermometer

Tympanic thermometers are NOT recommended for children under one year of age. These thermometers use infrared to take the temperature in your child’s eardrum. Always clean the thermometer tip before using and follow the manufacturer’s instructions carefully.

Ear Temperature
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  • Gently tug on the ear, pulling it up and back. This will help straighten the ear canal and make a clear path inside the ear to the eardrum.
  • Gently insert the thermometer until the ear canal is fully sealed off.
  • Squeeze and hold down the button for one second.
  • Remove the thermometer and read the temperature.
  • Fever is an ear temperature of 37.5°C (99.5°F).

Not recommended

Digital electronic pacifier thermometers and temperature strips are inaccurate and unreliable. Do not use these methods to take your child's temperature. Touching your child's forehead or neck may give you a hint that your child has a fever, but this is not a reliable way to check for fever. Confirm your suspicion of a fever by taking a true measurement using the methods explained above. 

Call your doctor or other health care provider if your child:

  • has a fever and is less than 6 months old.
  • has a fever for more than 72 hours (three days).
  • is very cranky and irritable.
  • is very sleepy and does not respond.
  • is wheezing or coughing.
  • has a fever and a rash or other unusual symptoms.

Key points

  • Putting a hand to the forehead is not a good way to find out if a child has a temperature.
  • The best way to take a temperature depends on a child’s age.
  • Always wash thermometers before and after taking a temperature.
  • Call your doctor if your child has a very high temperature, if your child has a temperature that last three days, or if your child has a temperature and is less than 6 months old.
  • Do not use a mercury-in-glass thermometer.

Converting Fahrenheit (°F) and Celsius (°C)

Temperatures are measured in degrees Celsius (°C) or degrees Fahrenheit (°F). The table below shows equivalent Celsius and Fahrenheit temperatures.  

°C °F
37°C 98.6°F
37.2°C 99°F
37.5°C 99.5°F
37.8°C 100°F
38°C 100.4°F
38.3°C 101°F
38.9°C 102°F
39.5°C 103°F
40°C 104°F
40.6°C 105°F
41.1°C 106°F
41.7°C 107°F

 

Elly Berger, BA, MD, FRCPC, FAAP, MHPE

4/3/2013




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