Skip to Main Content


Temperature can be measured by many methods. These include the following thermometers:

  • mercury thermometer (now superseded)

  • digital electronic pacifier

  • digital peak thermometer with LED light

  • digital infrared aural

  • electronic probe

  • forehead thermometer (temporal area).

The favoured general instrument for oral and rectal use is the digital peak-hold thermometer.

Table 19.1 gives a basic guide to interpreting the temperature values obtained.

Table 19.1Interpretation of temperature measurement

Basic rules of thermometer usage

Oral use

  1. Place under the tongue at the junction of the base of the tongue and the floor of the mouth to one side of the frenulum—the ‘heat pocket’.

  2. Ensure the mouth is kept shut.

  3. Remove dentures.

Note: Unsuitable for children 4 years and under, especially if irritable; use axilla or rectum.

Rectal use

A suitable route for babies and young children under the age of 4.1


  1. Lubricate the stub with petroleum jelly.

  2. Insert for 2–3 cm (1 inch).

  3. Keep the thermometer between the flexed fingers with the hand resting on the buttocks.

  4. Wipe rectal thermometers with alcohol and store separately from oral.

Fig. 19.1

Rectal temperature measurement


  • Dig thermometer in too hard.

  • Hold it too rigidly.

  • Allow the child to move around.

Axillary use1

Although unreliable, it is practical for young children and gives a helpful guide. If used it should be placed high in the axilla.

Groin use

This route is not ideal but is more reliable than the axilla. It closely approximates oral temperature.

In infants, the thigh should be flexed against the abdomen.

Vaginal use

Mainly used as an adjunct to the self-assessment of ovulation during the menstrual cycle. Should be placed deeply in the vagina before leaving the bed in the morning.

Infrared aural (ear drum) use2

The temperature can be measured in 3 seconds with an infrared device placed in the ear canal. Hold the child’s head firmly so that it does not move. There is much debate about its efficacy but it appears to be worthwhile as it is a simple method and in general practice the benefits of convenience outweigh possible lack of accuracy. The normal range is ...

Pop-up div Successfully Displayed

This div only appears when the trigger link is hovered over. Otherwise it is hidden from view.