Checking your temperature, here’s what you need to know.

Why measure body temperature?

Fever is the most common form of disease-related change in body temperature.  It is of great medical importance to measure body temperature.  The reason is that a change in body temperature goes together with a number of diseases.  Also, you can monitor the progress of certain diseases by measuring body temperature, and evaluate the efficiency of treatment given using the change in body temperature.

What is important to know in taking temperature?

  1. The measured body temperature always depends on where it is measured. Therefore, there is no simple “normal temperature”.
  2. A healthy person’s body temperature varies with hormone levels, activity, environmental exposure and time of the day. For example, rectal temperature is slightly higher at rest in the evening than in the morning, body temperature typically increases after physical activity or your body temperature will be lower morning after sleeping in a cold room.
  3. A temperature measurement differs between core temperature and surface temperature. The surface temperature is measured at the skin surface (for example forehead).  It is a mix between the body’s core temperature and the ambient temperature (air, room, environment).  The core temperature is measured by inserting a thermometer into a body cavity (for example rectum), which yields the temperature of the mucous tissue.  Body surface temperature measurements used clinically are the arm pit (axially measurement) and in the groin (inguinal measurement).  In both cases, press the respective limb against the body in order to reduce any ambient temperature influence.
  4. Do not confuse the technical accuracy of the thermometer itself with this accuracy in use (clinical accuracy).  Technical accuracy is determined under idealized conditions to guarantee the quality of the instrument, taking the relevant technical standards into account.  The human body temperature (clinical accuracy) depends on the measurement location, time and environment.  It may vary slightly due to physiological causes and are not due to a thermometer malfunctioning.  An accuracy of + 0.1°C can be considered state of the art for high-grade thermometers.  By correctly using a thermometer, the clinical accuracy can be strongly increased (follow the operating instructions!).

Where should I take body temperature?

You can take body temperature using the mouth (oral), anus (rectal), armpit or groin (axillary), ear (tympanic) or forehead (temporal).  Remember that temperature readings vary depending on which one you use, and you need an accurate body temperature to determine if a fever is present.

Oral measurement

An oral measurement can be taken as a buccal measurement (in the cheek) or as a sublingual measurement (under the tongue).  A sublingual measurement is preferable to a buccal measurement.  The normal oral temperature range is approximately between 35.5 °C and 37.5 °C.  The average normal oral temperature is 37°C.

Rectal measurement

Taking a rectal measurement is the most reliable way to obtain a core body temperature value.  Result variation with this type of measurement is low and the precision is particularly high.  The normal temperature range is approximately between 36.6 °C and 38.0 °C.  Rectal temperature is 0.3°C to 0.6°C higher than an oral temperature reading.  Rectal temperatures are generally thought to be the most accurate for checking a young child’s temperature.

Axillary measurement

Measuring the body’s surface temperature is normally conducted in the armpit and in the groin.  The normal axillary temperature range is approximately between 34.7 °C and 37.3 °C.  An armpit (axillary) temperature is usually 0.3°C to 0.6°C lower than an oral temperature.

Tympanic measurement

Infrared ear thermometers measure infrared energy radiated from the eardrum and the surrounding tissue.  Temperature differences between the opening of the ear canal and the tympanic membrane can be as much as 2.8°C.  To ensure accurate temperature measurements, position the tympanic thermometer probe to fit snugly in the ear canal.  An ear (tympanic) temperature is 0.3°C to 0.6°C higher than an oral temperature.

Temporal measurement

Non-contact forehead thermometer measures infrared energy radiated from the forehead.  A forehead (temporal) temperature reading is usually 0.3°C to 0.6°C lower than an oral temperature.

How do you get the best temperature reading?

Just as there are factors that determine our body temperature, there are factors that affect your temperature reading.  Here are tips for getting the best readings from the three most frequently used thermometers.

Oral thermometers

  • Avoid consuming hot or cold foods prior to taking your temperature.
  • Clean with soap and warm water or rubbing alcohol before using.
  • Place under the tongue and close your mouth for one minute before removing.

Tympanic or ear thermometers

  • Placement in the ear canal is important, make sure to get into the ear canal far enough.
  • Make sure the ear is clean, too much earwax can interfere with readings.
  • Be sure to read and follow the manufacturer’s directions carefully.

Temporal or forehead thermometers

  • Place the sensor on the centre of the forehead and slide toward the top of the ear until you get to the hairline.
  • Readings can be inaccurate if placement and motion is not carried out properly.  If the measurement seems off, try again.