Different Ways To Take Your Child’s Temperature (And When To Call A Doctor)

Understanding how to accurately take your child’s temperature, how different methods compare, and when a fever needs medical attention can help you respond to fevers appropriately and with confidence! 

This article walks through the main ways to take a child’s temperature and offers clear guidance on when to call a doctor.

I recommend that all parents have two thermometers at home! Things happen - batteries run out, and thermometers can be finicky. There are a lot of different thermometers on the market, so let’s take a look at the different options and how to use them.

You might like this article, too: Temperature Tamer™ or Nature Profen™: Choosing The Right Herbal Remedy For Your Child

Rectal temperature measurement is considered the most accurate way to assess a baby’s core body temperature. This method is especially important in infants, where fever thresholds are taken very seriously. In older kids, rectal temperature measurement is usually not needed, and a more comfortable method can be used. 

Be sure to disinfect the thermometer before and after each use by washing the tip with cold water and antibacterial soap, then wiping it down with a 70% isopropyl alcohol wipe.

• Have your child lie on their stomach across your lap, or on their back with legs pulled gently toward the chest.

• Apply a small amount of lubricant (I like coconut oil) to the thermometer tip.

• Insert gently into the anus no more than 1 inch.

• If baby is under 6 months old, insert no more than ½ inch.

• Stop if there is resistance or if baby seems to be in pain.

• Hold in place until the thermometer beeps.

A rectal temperature of 100.4°F (38°C) or higher is a fever.

Important safety note: Rectal temperatures should not be taken in children with leukemia, certain cancers, organ transplants, HIV, sickle cell disease, or other conditions affecting the immune system.

Oral temperatures can be accurate in older children who are able to cooperate fully. This generally applies to children around four or five years old and up.

The thermometer should be placed under the tongue with the mouth closed until the reading is complete. Eating or drinking shortly before checking can affect accuracy, so it’s best to wait at least 15-30 minutes after eating or drinking before taking a temperature.

A fever is usually defined as 100°F (37.8°C) or higher when measured orally.

Underarm temperatures are easy to take and gentle, making them appealing for frequent checks or for children who resist other methods. However, axillary readings tend to run lower than core body temperature, and they are not super reliable. 

For a reliable underarm temperature reading, follow these steps:

• Ensure the armpit is dry.

• Place the tip high in the armpit.

• Hold the arm tightly against the chest.

• Keep in place until it beeps.

An underarm temperature of 99°F (37.2°C) or higher is considered a fever.

If you measure a temperature under the arm of a baby under 3 months and it is 99°F or higher, you should confirm with a rectal temperature immediately.

Ear thermometers measure infrared heat from the eardrum and can give quick results. They are generally considered appropriate for children over six months of age.

Be sure to clean the thermometer by following the manufacturer’s instructions between uses, typically wiping the probe with an alcohol swab or using a disposable probe cover if provided. This helps prevent the spread of germs and ensures more accurate readings.

Accuracy depends heavily on proper placement and a clear ear canal. Earwax, small ear canals, or incorrect positioning can lead to falsely low or high readings. For the most reliable tympanic reading, follow these steps: 

• Pull the ear back and down for infants under 1 year.

• Pull back and up for children over 1 year.

• Aim the probe toward the opposite eye.

• Hold it in place until it beeps.

Because technique matters so much for an accurate reading, ear thermometers work best in children who can sit relatively still and tolerate proper placement.

For slide thermometers:

• Place the sensor at the center of the forehead.

• Keep in contact with skin.

• Slowly slide toward the top of the ear.

• Stop at the hairline.

For no-touch models:

• Hold less than 1 inch from the forehead.

• Do not move during measurement.

Personally, I use this slide thermometer at home. I’ve found it to be more reliable than other forehead options.

The forehead kiss method is not a medically accurate way to take your kid’s temperature. That said, parental instinct is important. If you feel like your child is warm or acting off, or something is wrong, that should be taken seriously! Always double check with a thermometer, but don’t dismiss your instincts if you feel like something is wrong. 

In most cases, a fever is simply a sign that your child’s immune system is doing its job - but there are times when fever requires prompt medical attention (1).

Call your pediatrician right away if your baby is under three months old and has a temperature of 99°F (37.2°C) when measured using the axillary method, or 100.4°F (38°C) or higher when using the rectal method. Immediate evaluation is also important if your child is unusually hard to wake, very floppy, struggling to breathe, showing signs of dehydration, or if fever is accompanied by a stiff neck, severe headache, or persistent vomiting.

You should contact your child’s doctor within 24 hours if a fever lasts more than two to three days, keeps returning, or is accompanied by worsening pain or symptoms. It’s also appropriate to call anytime you’re unsure or concerned - parental intuition is an important part of pediatric care.

Looking for herbal support for occasional temperatures? Check out our Temp Tamer™ line. You might like this article, too: FAQ: Can My Child Take Motrin® or Tylenol® with Temperature Tamer™ or Nature Profen™?

A high temperature can feel scary in the moment, but most of the time it’s simply a sign that your child’s immune system is responding exactly as it should! There are many thermometer options, and knowing which thermometer to use, how to use it correctly, and what temperatures to look out for allows you to respond calmly instead of reactively. Pair accurate measurement with careful observation - how your child is breathing, drinking, interacting, and behaving overall - and you’ll have a much clearer picture of what’s going on. And remember, if your baby is under three months old or something about your child’s condition worries you, it’s always appropriate to call your pediatrician.

1. Balli S, Shumway KR, Sharan S. Physiology, Fever. 2023 Sep 4. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan–. PMID: 32966005.