How To Take Your Child’s Temperature

When your child is running a fever, it’s a sign that their body is trying to fight an infection¹. A child’s age determines the best way to take their temperature – for children under age 2, the rectal method is first choice and axillary (armpit) second; for ages 2-5, the rectum, ear, or armpit; while the oral method is first choice for over-5s able to hold the thermometer under their tongue for long enough^2,3.

The axillary (armpit) method is usually used to screen whether or not a child has a fever – but if it signals a high temperature, it should be rechecked with a more accurate oral or rectal reading, according to the child’s age^3,4.

You can treat an older child at home, providing you give enough liquids and they appear generally well². See your child’s healthcare provider if the fever lasts for more than 72 hours².

A word about babies and toddlers…

Babies aren’t yet able to regulate their body temperature and toddlers are also more sensitive to temperature⁵. Your baby or toddler may have a high temperature if they show signs such as feeling hotter to the touch, on their forehead, back or stomach, feeling sweaty, or having flushed cheeks¹. Babies younger than six months must see a healthcare provider when they have a fever². 

What type of thermometer should I use?

Digital thermometers use electronic heat sensors to record body temperature and can be used in the rectum (rectal), mouth (oral) or armpit⁶. They work much faster than the old mercury thermometers and are more accurate^3,4. Oral and rectal digital thermometers have different shapes and you should never substitute one for the other⁴. Using an oral thermometer in the rectum can cause injury – so rectal thermometers have a security bulb designed specifically for taking the temperature safely⁴.

Warning: Never use an old-fashioned glass thermometer^1,4,6. These can break, releasing glass splinters and poisonous mercury¹.

Ways to take a temperature

In all cases, first check that the digital thermometer is switched on⁶.

Rectal (in the rectum)

Coat the tip of the clean thermometer with petroleum jelly⁶. Put your baby tummy down, holding them in place with one hand^4,6. Or put them face-up, bend their legs towards their chest and secure them by holding the back of the thighs with one hand³. Insert the thermometer gently ±1,3 cm – 2,5cm into the rectum^4,6. Don’t force it if you feel resistance³. Hold the thermometer steady until it beeps (usually ±30 seconds), then remove and check the reading³.

Oral (by mouth)

Place the end of the clean thermometer under the back of the tongue⁶. Leave it there until it beeps. Remove the thermometer and check the reading. Always wait until at least 15 minutes after eating or drinking to take an oral reading⁶.

Axillary (under armpit)

Place the digital thermometer under the child’s armpit, touching the skin, not the clothing⁶. While taking the temperature, hug your child so their arm is tucked tightly against their body until you hear the beep, at which point you can remove the thermometer and read the temperature⁶.

Tympanic (in the ear)

Although this method is quick, it can give inaccurate readings if inserted incorrectly¹. Always read the manufacturer’s instructions so you insert the thermometer the correct distance into the ear canal⁶. Hold it in place firmly until you hear the beep⁶.  You can then read the temperature⁶.

Temporal artery (forehead)

This newer method, which measures the temperature of blood flowing through the temporal artery, is considered very accurate⁵. It’s also more comfortable than a rectal thermometer and more calming for babies⁵. You place the thermometer sensor in the middle of your child’s forehead and then press and hold the scan button⁵. Keep the thermometer in direct contact with the skin while you slowly move it across their forehead towards the top of the ear⁵. Stop at the hairline before removing the thermometer and reading the temperature⁵.

Tip: Clean the thermometer with warm, soapy water before and after using³.Don’t bundle up your child too tightly beforehand, check that they’ve not been in a very warm room, been very active, and don’t have a hot water bottle against their body¹. Never leave a child unattended with a rectal thermometer inserted⁴.

What is a normal temperature?²

Method	Normal temperature range
Rectum	36,6 °C – 38 °C
Mouth	35,5 °C – 37,5 °C
Armpit	36,5 °C – 37,5 °C
Ear	35,8 °C – 38 °C

References

1. NHS. Staff overview. How to take your baby’s temperature. Available at https://www.nhs.uk/conditions/baby/health/how-to-take-your-babys-temperature/
2. Canadian Pediatric Society. Staff overview. Fever and Temperature Taking. Available at https://caringforkids.cps.ca/handouts/health-conditions-and-treatments/fever_and_temperature_taking
3. Cleveland Clinic. Staff overview. Thermometers: How to Take your Temperature. Available at https://my.clevelandclinic.org/health/articles/9959-thermometers-how-to-take-your-temperature
4. Johns Hopkins Medicine. Staff overview.  Measuring a Baby’s Temperature. Available at https://www.hopkinsmedicine.org/health/conditions-and-diseases/measuring-a-babys-temperature
5. NHS North East Essex Clinical Commissioning Group. Staff overview. Staying well in hot weather – tips for parents and guardians. Available at https://www.neessexccg.nhs.uk/stay-well-summer-children
6. Mayo Clinic. Staff overview. Thermometer basics: Taking your child’s temperature. Available at https://www.mayoclinic.org/healthy-lifestyle/infant-and-toddler-health/in-depth/thermometer/art-20047410