General Guidelines on measuring Types of thermometer and
body temperature and using specific precautions
thermometer Description Special points to note*
Mercury-in-glass/ Alcohol-in-glass Thermometer
Measures oral, As mercury spill is hazardous to
1. Compare the accuracy, suitability, rectal or armpit environment and health, the use of
convenience and price of thermometers body temperature mercury thermometer should be
before purchase. through the avoided as far as possible.
thermal
2. Choose a thermometer and method of Thermometer should be reset by
expansion of
measurement which suit the individual‘s shaking the mercury/ ethanol level
mercury/ ethanol
age and health condition; Consult down below 35°C (95°F) each time
healthcare professionals if in doubt. Oral
before using.
3. Patients with communicable diseases The tips of oral thermometer and
should use personal thermometers to rectal thermometer are different in
shape (slender vs. round) and must
avoid cross-infection.
Rectal not be cross-used. Proper use of
4. Familiarise with the correct use of
thermometer and temperature reading Electronic (digital) Thermometer thermometers to
by referring to the user instructions Measures oral, Temperature difference among oral,
provided by manufacturer.
rectal or armpit rectal and armpit body temperature measure body
5. Avoid activities that would distort body temperature should be noted.
temperature measurement (e.g. by means of temperature
drinking hot water immediately before thermistor with its
taking oral temperature). resistance varying
according to the
6. Clean and maintain the thermometer temperature
according to the procedures
recommended by the user instructions.
Infrared Thermometer
7. In case body temperature needs to be
taken regularly, take the temperature at Measures thermal For ear thermometer, a new ear-probe
the same time of each day and use the radiation jacket should be used for different
same temperature taking method to (infrared) emitted person; the ear canal must be pulled
allow comparison. from ear and straight when measuring.
forehead to infer
8. If there is any doubt about the body Forehead thermometer should only be
body temperature
temperature reading, please consult used for screening instead of
healthcare professionals. diagnostic purpose due to greater
measurement error.
* Users should read and follow the instructions in the user
Medical Device Control Office
manual of the thermometer because operation procedures
E-mail : mdco@dh.gov.hk
may vary among brands Website : www.mdco.gov.hk
Thermometer can be Comparison among different measurement methods
used to check the body
temperature to see Measurement method Oral Ear Rectal Forehead Armpit
whether a person has a Suitability
fever. This pamphlet
provides an introduction Infants and children below 6
to body temperature, its
measurement methods
Cooperative
Adults and
and proper use of various
types of thermometer.
children Uncooperative
above 6
Unconscious
Accuracy ☺☺☺ ☺☺☺ ☺☺☺ ☺ ☺☺
Convenience and speed ☺☺☺ ☺☺☺ ☺ ☺☺☺☺ ☺☺
> 37.5°C > 38°C > 38°C > 36°C > 37.3°C
Reference level for fever
(99.5°F) (100.4°F) (100.4°F) (96.8°F) (99.1°F)
Body Temperature Measurement methods and specific precautions
There are two ways to measure body temperature —
by measuring core temperature and surface Measurement method Unsuitable conditions for the measurement method
temperature.
Oral ● Suffering from shortness of breath
Body Meaning Measurement
● Sneezing repeatedly, having a hard cough or suffering a seizure
3
temperature taken through ● Unconscious or confused
measurement ● Unable to close the mouth tightly
Core Temperature of Oral cavity, ear Having a middle ear infection
temperature deep tissues canal, rectum Ear ●
● Obstruction of ear canal by ear wax Infrared ear
Surface Temperature of Forehead, armpit ● Wearing hearing aid thermometer
temperature surface skin
tissues Rectal ● Large amount of faeces accumulated in the rectum
Since surface temperature is more susceptible to
● Rectal diseases, e.g. haemorrhoid or diarrhoea, etc.
changes in the surroundings, it is considered less
accurate and is recommended for use only when ● Just undergone intestinal operation
there is difficulty in measuring the core temperature. ● Having wounds/ lesions in the anus
Armpit ● Unable to secure thermometer under the axilla
Forehead ● Forehead being covered (e.g. by bandage/ cooling gel sheet)
Infrared forehead
thermometer