Clinical thermometer

Oral

• Oral temperature may only be taken from a patient who is capable of holding the thermometer securely under the tongue, which generally excludes small children or people who are unconscious or overcome by coughing, weakness, or vomiting. (This is less of a problem with fast-reacting digital thermometers, but is certainly an issue with mercury thermometers, which take several minutes to stabilise their reading.) If the patient has drunk a hot or cold liquid beforehand time must be allowed for the mouth temperature to return to its normal value.
• The typical range of a sub-lingual clinical thermometer for use in humans is from about 35 °C to 42 °C or 90 °F to 110 °F.

Armpit

• The armpit (axilla) temperature is measured by holding the thermometer tightly under the armpit. One needs to hold the thermometer for several minutes to get an accurate measurement. The axillary temperature plus 1 °C is a good guide to the rectal temperature in patients older than 1 month.The accuracy from the axilla is known to be inferior to the rectal temperature.

Rectal

• Rectal thermometer temperature-taking, especially if performed by a person other than the patient, should be facilitated with the use of a water-based personal lubricant.