Fever - How to Take the Temperature  

When Does Your Child Have a Fever?

  • Rectal, Forehead or Ear temperature: 100.4 F° (38.0° C) or higher
  • Oral (Mouth) temperature:  100° F (37.8° C) or higher
  • Under the arm (Armpit) temperature:  99° F (37.2° C) or higher
  • Caution: Ear temperatures are not accurate before 6 months of age

Where to Take the Temperature

  • Rectal temps are the most accurate. Forehead temps are the next most accurate. Oral and ear temps are also accurate if done properly. Temps done in the armpit are the least accurate. Armpit temps are useful for screening at any age.
  • Age under 3 months old (90 days old).
    An armpit temp is the safest and is good for screening. If the armpit temp is above 99° F (37.2° C), re-check it. Use a rectal or forehead reading. Reason: If young babies have a fever, they need to see a doctor now. New research shows that forehead temps are accurate under 3 months of age.
  • Age under 4 or 5 years old. Rectal, forehead, or pacifier temps are accurate. An ear thermometer can be used after 6 months old. An armpit temp is good for screening if it is taken right.
  • Age over 4 or 5 years old.
    Safe to take the temp orally (by mouth). Ear and forehead thermometers are also good.

How to Take Rectal Temperatures

  • Age: Birth to 4 years old
  • Have your child lie stomach down on your lap.
  • Put some petroleum jelly on the end of the thermometer and the anus.
  • Slide the thermometer gently into the anus for about 1-inch. If your child is less than 6 months old, put it in only about ½ inch. That means until you can no longer see the silver tip.
  • Hold your child still. Leave a digital thermometer in for about 20 seconds. (Note: The AAP suggests that older glass thermometers be replaced. They contain mercury. If that's all you have, leave it in for about 2 minutes.)
  • Your child has a fever if the rectal temp is above 100.4° F (38° C).

How to Take Armpit Temperatures

  • Age: Any age for screening
  • Put the tip of the thermometer in an armpit. Make sure the armpit is dry.
  • Close the armpit by holding the elbow against the chest. Do this for 4 or 5 minutes or until your digital thermometer beeps. The tip of the thermometer must stay covered by skin.
  • Your child has a fever if the armpit temp is above 99.0° F (37.2° C). If you have any doubt, take your child's temp by rectum or forehead.

How to Take Oral Temperatures

  • Age: 4 years and older
  • If your child had a cold or hot drink, wait 30 minutes.
  • Put the thermometer under one side of the tongue towards the back. It's important to put the tip in the right place.
  • Have your child hold the thermometer with his lips and fingers. Don't use the teeth to keep in place. Keep the lips sealed. Keep a digital thermometer there for about 30 seconds or until it beeps. (Note: The AAP suggests that older glass thermometers be replaced. They contain mercury. If that's all you have, leave it in for about 3 minutes.)
  • Your child has a fever if the temp is above 100° F (37.8° C).

How to Take a Digital Pacifier Temperature

  • Age: Birth to 1 year
  • Have your child suck on the pacifier until you hear a beep.
  • This takes 3 to 4 minutes.
  • Your child has a fever if the pacifier temp is above 100° F (37.8° C).

How to Take an Ear Temperature

  • Age: 6 months and older (not accurate before 6 months)
  • This thermometer reads the heat waves coming off the eardrum.
  • A correct temp depends on pulling the ear backward. Pull back and up if over 1 year old.
  • Then aim the tip of the ear probe between the opposite eye and ear.
  • Parents like this thermometer because it takes less than 2 seconds. It also does not need the child to cooperate. It does not cause any discomfort.
  • Caution. Being outdoors on a cold day will cause a low reading. Your child needs to be inside for 15 minutes before taking the temp. Earwax, ear infections and ear tubes do not keep from getting correct readings.

How to Take a Forehead (Temporal Artery) Temperature

  • Age: Any age
  • This thermometer reads the heat waves coming off the temporal artery. This blood vessel runs across the forehead just below the skin. 
  • Place the sensor head at the center of the forehead.
  • Slowly slide the thermometer across the forehead toward the top of the ear. Keep it in contact with the skin. 
  • Stop when you reach the hairline.  
  • Read your child’s temp on the display screen.
  • Used in more doctor's offices than any other thermometer.
  • Parents like this thermometer because it takes less than 2 seconds. It also does not need the child to cooperate. It does not cause any discomfort.
  • Caution: Forehead temperatures must be digital. Forehead strips are not accurate.

Author and Senior Reviewer: Barton D. Schmitt, M.D.

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