How to use a thermometer

Which thermometer you use, and how you use it, depends on the age of your child. There are many types of thermometers available.

Digital thermometers are the most common. You can use these for tamariki (children) of any age. They are easy to use and accurate and are usually the cheapest.

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Electronic ear thermometers are expensive and are less accurate in small pēpi (babies).

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Infrared forehead thermometers are quick and easy to use, as you simply point them at your child's forehead. But, they are expensive and may not be accurate. They measure the forehead skin temperature which changes a lot with blood flow and room temperature.

You can use a digital thermometer for your child (or adult) of any age. A digital thermometer gives a digital reading. There are a number of brands. They are usually the cheapest option. You need to read and follow the instructions that come with your thermometer.

Use a digital thermometer under your child's arm if they are under 5 years of age

If your child is under 5 years, you can use the digital thermometer under your child's arm. If you measure the temperature under their arm, it records about 0.5 to 1 degree Celsius lower than the core temperature.

To use a digital thermometer under the arm (the axillary temperature):

• Turn it on (these thermometers usually have a button you press to turn on).
• Place the end in the armpit against the skin, and bring your child's arm down over the top of it – it often helps to hug your child to keep the arm down and the thermometer in place.
• Most thermometers beep when they have finished measuring your child's temperature.
• Some thermometers also beep while measuring and the beep changes when the thermometer has finished measuring your child's temperature – to avoid confusion, it's worth keeping the thermometer in place for 2 minutes.
• Remove the thermometer and read the number on the side – the temperature you read is about 0.5 to 1 degree Celsius lower than your child's actual body or core temperature.
  
  

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Measure your child's temperature in their mouth if they are 5 years of age or older

If your child is 5 years of age or older you can try to measure the temperature in their mouth (the oral temperature). Make sure you only use a digital thermometer in your child's mouth.

To use it in the mouth in older tamariki:

• Your child has to be able to cooperate, which usually means they are of school age.
• Turn it on.
• Place the end in the mouth under the side of the tongue – try to get your child to keep it there.
• Some thermometers make beeping noises when they have finished, but it is worth keeping it in place for at least 2 minutes.
• Remove the thermometer and read the number on the side – the temperature you read in degrees Celsius is close to your child's actual body or core temperature.
  
  

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The electronic or infrared ear thermometer is fast and accurate if used correctly. You can use it in older children and adults, but not in young babies. There are a number of brands. They are more expensive than digital thermometers.

Read the instructions for your thermometer to find out how to turn it on and take the reading. When placing the measuring end in the ear, be gentle. You don't have to push it far into the ear canal, just at the entrance.

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Plastic strip thermometer

These are plastic strips that you place on the person's forehead – they are not accurate so it's best not to use them.

Mercury-in-glass thermometer

These old style thermometers are no longer available but some households still have them. Mercury vapour can be toxic if the thermometer breaks, so don't use these thermometers. Consider getting a digital thermometer instead.

Body temperature by itself does not tell you how sick your child is. Regardless of whether your child has a fever or not, if you think they are unwell and you are worried, see your healthcare provider. 

In pēpi (babies), an unstable body temperature is very worrying – see your healthcare provider if your baby has either a high or low temperature.

Why should I take my child's temperature?

• You might want to measure your child's body temperature if they feel hot. If they don't seem unwell, you don't need to take their temperature.
• The most common reason for a child to have a raised temperature is because they are fighting off an infection.
• If your child is very young (under 3 months of age) and they have a fever, see your healthcare provider.

What am I measuring?

When you take a temperature, you are trying to measure how hot your child is inside their body. This is called their 'core temperature'.

You measure the temperature in places that are closest to the inside temperature:

• inside the mouth (oral)
• under the arm (axillary)
• in their outer ear canal (tympanic).

Should I measure my child's temperature in their bottom?

In hospital, doctors and nurses sometimes measure temperatures in children's bottoms – they take a rectal temperature. Don't take your child's temperature this way at home. 

What's a normal temperature?

The normal temperature inside your child's body is about 37°C. Your child's brain helps control their core temperature and to keep it around that level.

After 3 months of age, body temperature changes with a daily rhythm – rising toward the end of the day before dropping overnight and then slowly coming up to about 37 in the morning.

What temperature indicates a fever?

A fever is when the temperature is more than 38°C. A fever by itself doesn't indicate whether your child is seriously sick or not.