What is the best way to measure for a fever?

A fever is a warning that something out of the ordinary is going on within your body, and the most common cause is an infection.1

From a medical point of view, a fever is when your body temperature rises above your normal level, which is around 37oC. It can vary throughout the day, and can be different in women, at different times of the menstrual cycle, while older people tend to have slightly lower body temperatures than young people.1

To be a little more specific, the Australian Department of Health defines fever as 38oC or higher.2

The best way to measure or monitor a fever of course, is a thermometer – but what sort of thermometer is best?

In broad terms, thermometers fall into two categories – contact or touch thermometers and remote or non-contact thermometers.3 Within those categories you’ll find different types, depending on their method of measuring.

Contact thermometers

The most common type of contact thermometers use electronic heat sensors to measure the body temperature. And they can be used orally (in the mouth), under the armpit, or rectally. They’re usually fast and generally have a digital display and beep when the reading has been completed, making them good for unwell children.

Readings taken rectally provide the most accurate readings for infants, especially those 3 months or younger, as well as children up to age 3.3

Axillary readings (taken from the armpit) are usually the least accurate.3

Oral readings are usually accurate for older children and adults, but it’s important that the mouth is kept closed until the reading is complete.3

Health professionals recommend using different thermometers for rectal and oral use for hygiene reasons.3

There are non-digital types of contact thermometers, such as strips that are placed on the forehead. While convenient, they aren’t as accurate as a ‘real’ thermometer.4 The old-fashioned glass mercury thermometers are not recommended because if they break, they release a highly toxic chemical (mercury) that is quite dangerous.3

Remote or non-contact thermometers

Remote thermometers use infra-red beams and technology to measure the temperature and can provide a quick measurement.3

The two most common types are used either on the forehead (known as temporal artery thermometers) or in the ear (known as tympanic thermometers).

Infrared tympanic or ear thermometers are a reasonably comfortable and quick option for children and are best designed for infants older than age 6 months, older children and adults.3

Remote forehead thermometers became particularly popular during the pandemic to avoid close contact while still providing accurate readings.

Welcare offers some very affordable digital thermometers.

* Always read the label and follow the directions for use.


  1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7195085/
  2. https://www.healthdirect.gov.au/fever
  3. https://www.mayoclinic.org/diseases-conditions/fever/in-depth/thermometers/art-20046737
  4. https://www.parents.com/health/fever/the-best-way-to-take-a-temperature/



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