• Medical Author:
    John P. Cunha, DO, FACOEP

    John P. Cunha, DO, is a U.S. board-certified Emergency Medicine Physician. Dr. Cunha's educational background includes a BS in Biology from Rutgers, the State University of New Jersey, and a DO from the Kansas City University of Medicine and Biosciences in Kansas City, MO. He completed residency training in Emergency Medicine at Newark Beth Israel Medical Center in Newark, New Jersey.

  • Medical Editor: Melissa Conrad Stöppler, MD
    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

Quick GuideSore Throat or Strep Throat? How to Tell the Difference

Sore Throat or Strep Throat? How to Tell the Difference

How do health-care professionals diagnose a fever?

Along with having generalized symptoms of a fever, taking one's temperature with a thermometer can confirm the diagnosis of a fever. A temperature greater than 100.4 F in adults or children is considered a fever.

Different tests may be done by a doctor, such a blood and imaging tests, to determine the cause of a fever and if the cause of the fever needs to be treated.

How should someone take a temperature for fever?

Digital thermometers can be used to measure rectal, oral, or axillary (under the armpit) temperatures. The American Academy of Pediatrics does not recommend use of mercury thermometers (glass), and they encourage parents to remove mercury thermometers from their households to prevent accidental exposure to this toxin.

Measuring an axillary (under the armpit) temperature for fever

Axillary temperatures are not as accurate as rectal or oral measurements, and these generally measure 1 degree lower than a simultaneously obtained oral temperature.

  • Place the tip of the digital thermometer in a child's armpit.
  • Leave the thermometer in place about one minute or until one hears a beep to check a digital reading.

Measuring fever by eardrum temperature

Tympanic (ear) thermometers must be placed correctly in a child's ear to be accurate. Too much earwax can cause the reading to be incorrect.

Eardrum temperature measurements are not accurate in small children and should not be used in children under 3 years (36 months) of age. This is especially true in infants below 3 months of age when obtaining an accurate temperature is very important.

Measuring fever by oral temperature

People 4 years old and older can have their temperature taken with a digital thermometer under the tongue with their mouth closed.

  • Clean the thermometer with soapy water or rubbing alcohol and rinse.
  • Turn the thermometer on and place the tip of the thermometer as far back under the tongue as possible.
  • The mouth should remain closed, as an open mouth can cause readings to be inaccurate.
  • The thermometer should remain in place for about one minute or until one hears the beep. Check the digital reading.

Avoid hot or cold drinks within 15 minutes of oral temperature measurement to ensure correct readings.

Measuring fever by rectal temperature

The American Academy of Pediatrics recommends rectal temperature measurements for children and toddlers under 3 years of age, as this gives the most accurate reading of core temperature.

  • Clean the thermometer with soapy water or rubbing alcohol and rinse with cool water.
  • Use a small amount of lubricant, such as petroleum jelly, on the end.
  • Place the child or baby prone (belly-side down) on a firm surface, or place a child face up and bend his legs to his chest.
  • After separating the buttocks, insert the thermometer approximately ½ to 1 inch into the rectum. Do not insert it too far.
  • Hold the thermometer in place, loosely keeping one's hand cupped around the child's bottom, and keep one's fingers on the thermometer to avoid it accidently sliding further into the rectum. Keep it there for about one minute, until one hears the beep.
  • Remove the thermometer, and check the digital reading.
  • Label the rectal thermometer so it's not accidentally used in the mouth.

A rectal temperature will read approximately 1 degree higher than a simultaneously obtained oral temperature.

Medically Reviewed by a Doctor on 12/1/2016

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