Your baby's fever: How do I take the temperature?

How you take your child’s temperature will depend on your child’s age.

• According to the Canadian Paediatric Society (CPS), the preferred method of taking temperature in a child under two years of age is a rectal temperature.
• Second choice in children under two years of age is an axillary (armpit) reading.
• For children between the ages of two and five, alternate methods to rectal temperature include ear or axillary. After age five, an oral temperature is accurate.
• Make sure you are using the correct device. In other words, don’t use an oral thermometer if you are taking a rectal temperature and vice versa.

The Canadian Paediatric Society has the following tips:

• An oral thermometer doesn’t usually work in children younger than five, simply because it is too hard for them to hold the thermometer in place.
• While the axillary method is usually reliable, if you are convinced your child has a temperature and this method does not confirm it, it might be best to repeat the measure with a different method. With young children, using the armpit may be difficult because it’s hard to hold the thermometer in place with the arm closed tightly around the thermometer.
• Ear thermometers can be complicated to use and are not suggested for use in children under two. Sometimes it is hard to get a seal in a young child’s ear with the probe, and the temperature might be underestimated.

What do I do next? 

The degree of a fever does not always indicate the severity of the illness. I always tell my patients to watch how the child is behaving. A child who is lethargic is often of more concern than a child who seems his/her usual self. Your doctor will want to know the history of the fever and will ask several questions:

• When did the fever start?
• How long has the fever been present?
• Are there related symptoms such as a cough, headache and sore throat?
• Has there been anyone else sick at home or has your child been with any contacts that are known to be ill?
• Can your child eat or drink?
• Are there any known underlying illnesses?
• Was the child given an immunization in the past few days?

The degree of the fever does not always indicate the severity of the illness.

Normal temperature range:

• Rectum 36.6°C to 38°C (97.9°F to 100.4°F)
• Mouth 35.5°C to 37.5°C (95.9°F to 99.5°F)
• Ear 35.8°C to 38°C (96.4°F to 100.4°F)
• Armpit 34.7°C to 37.3°C (94.5°F to 99.1°F)