What’s the Best Way to Take Your Child’s Temperature? Here’s Why Their Age Matters
Key takeaways:
A fever is a temperature of 100.4°F or higher. In infants and children, there are different ways to get a temperature reading.
Using a rectal thermometer is the most accurate way to measure an infant’s temperature. It’s easiest to use a rectal thermometer for children under 3 years old.
Children over the age of 4 can use other temperature-taking methods like oral or in-the-ear thermometers.
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One of the scariest things a parent can experience is when their child is ill and has a high fever. It’s natural to wonder if your thermometer is accurate and a true reflection of your child’s body temperature. After all, it does matter how you measure your child’s temperature. And the right method can vary based on their age.
Here, we’ll review the best way to take a child’s temperature and how to know if it’s accurate.
What is a fever?
A fever is a raised body temperature of 100.4°F or more, when measured rectally. It’s the body’s way of fighting off an illness or infection. A normal body temperature varies from person to person and by the time of day. But the average body temperature should be around 98.6°F.
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The body temperature that’s considered a fever will vary based on how you take your child’s temperature. That’s because you can expect different temperature readings from different parts of the body. In general, a fever is considered to be 1°F to 1.5°F above your normal body temperature. This could look like the following temperatures or higher:
Rectal temperature of 100.4°F
Oral (mouth) temperature of 100°F
Under the arm (armpit) temperature of 99°F
Forehead temperature of 100°F
Ear temperature of 100.4°F
What’s the most accurate way to take a child’s temperature?
The most accurate way to take your child’s temperature will vary based on their age. The most common ways to measure temperature include:
Rectal: This is the best way to measure a child’s temperature as an infant to 3 years old.
Oral: This is best for children 4 years and older who are able to hold the thermometer under their tongue properly. Be sure to wait at least 15 minutes after eating or drinking for more accurate results.
Forehead: This method can be used for children of any age. Recent exposure to the sun or cold temperatures may affect accuracy.
Armpit: This is often an inaccurate way to measure temperature. But it can be used as a quick screening in school-aged children.
Ear: This is an option for children aged 6 months or older. Cold temperatures outside can affect accuracy. Be sure to wait at least 15 minutes after coming indoors.
If you think your child has a fever, always take their temperature with a thermometer. Feeling the forehead or other parts of the body is not a reliable way to check for fever.
What type of thermometer is best to use?
According to the American Academy of Pediatrics (AAP), a digital thermometer is the easiest to use and read. It shows the temperature in numbers and can be used in various places on the body. The three types of digital thermometers include:
Digital multi-use thermometer: This can measure a temperature in the rectum, mouth, or armpit. It’s important to label your thermometer so it isn’t used in both the rectum and the mouth.
Temporal artery thermometer: This is designed to measure the level of heat coming from blood vessels under the skin of the forehead. It can be used without touching the skin, which helps decrease the passing of germs. But these thermometer types are not always reliable because environmental factors may affect the reading.
Tympanic thermometer: This measures the temperature in a child’s ear using the heat coming from the eardrum. It’s best used in children over 6 months old. The accuracy depends on how wide the ear canal is and correct placement in your child’s ear.
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You’ll want to avoid using forehead fever strips because they are not reliable. They measure skin temperature, not body temperature.
You should also not use a mercury thermometer. These have a silver liquid inside and are dangerous if they break. That’s because mercury is poisonous if you come in contact with it. If you have a mercury thermometer at home, you should find an approved place to dispose of it. You can check your local recycling and disposal sites.
What is the correct way to take a baby’s rectal temperature?
Using a rectal thermometer is safe and easy for infants and young children. Always follow the cleaning instructions on the package before and after using a rectal thermometer. To use a rectal thermometer, follow these steps:
Put petroleum jelly on the tip.
Lay your child face down on a flat surface or your lap. Never leave them unattended.
Spread their buttocks and insert the bulb end about 1/2 inch to 1 inch (1 cm to 2.5 cm) into their anus. You will not damage anything inside or cause discomfort. Just don’t force the thermometer in or push it more than 1 inch.
Remove it once a temperature is displayed or when the device beeps, usually less than 1 minute.
When should you contact a provider about your child’s temperature?
Many times, a fever is nothing to worry about and will resolve on its own. But there are some warning signs to be aware of. You should contact your healthcare provider right away about a fever that’s:
100.4°F or higher in a child under 3 months of age
Over 104°F in any child
Lasting longer than 3 days
You should also contact your provider if your child has a fever and other symptoms or issues like:
A seizure (febrile seizure)
Vomiting, diarrhea, or abdominal pain
A rash, difficulty breathing, or a stiff neck
Looks very ill, is very fussy, or does not respond normally
A weakened immune system (like sickle cell disease or cancer)
The bottom line
As a parent, fever in your child can be scary. But keep in mind that it’s a sign the body is doing its job to fight off an infection. In the meantime, a good way to monitor for fever is to use a digital thermometer in the mouth, rectum, or ear. There are many ways to take a temperature, but a rectal temperature is best for children under the age of 4. Using a thermometer on the forehead or armpit can be used for older kids, but it’s unreliable at times. If you’re unsure of the best way to take your child’s temperature, talk to your provider for guidance.
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References
Chaturvedi, D., et al. (2003). Reliability of perception of fever by touch. Indian Journal of Pediatrics.
Del Bene, V. E. (1990). Chapter 218 temperature. Clinical Methods: The History, Physical, and Laboratory Examinations. 3rd edition.
Healthychildren.org. (2020). How to take your child's temperature. American Academy of Pediatrics.
InformedHealth.org. (2019). Fever in children: When to see a doctor. Institute for Quality and Efficiency in Health Care (IQWiG).
Lewit, E. M., et al. (1982). An evaluation of a plastic strip thermometer. Journal of the American Medical Association.
MedlinePlus. (2022). Temperature measurement.
Mogensen, C. B., et al. (2018). Forehead or ear temperature measurement cannot replace rectal measurements, except for screening purposes. BMC Pediatrics.
U.S. Environmental Protection Agency. (2023). Mercury thermometers.
Wyckoff, A. S. (2009). Thermometer use 101. AAP News.
