What is body temperature?
Body temperature is one of the core 'observations' or 'vital signs' that reflects the balance between heat production and heat loss within the body. It is measured in degrees Celsius (°C) or Fahrenheit (°F).
The average adult's normal body temperature hovers around 37 degrees Celsius (98.6 degrees Fahrenheit) but like blood pressure, individual variation exists with a range from 36.1°C (97°F) to 37.2°C (99°F).
Temperature can also vary slightly depending on the time of day, activity level, and other factors. It is a useful marker to measure, especially when we are feeling unwell to confirm if there is fever. In some instances, our body temperature can drop too low and when extreme, this is called hypothermia.
Why is it useful to measure body temperature?
Measuring body temperature can help to:
- Detect an infection: When you have an infection, your body temperature will often rise. This is because your body is fighting off the infection and trying to raise the temperature of your body to make it more difficult for the bacteria or virus to grow.
- Identify other health problems: Sometimes, a high or low body temperature can be a sign of an underlying health problem, such as a thyroid disorder.
How do you measure body temperature?
There are several ways to measure your body temperature. The most common methods include:
Oral thermometer:
This is one of the commonest types of thermometers. Place the thermometer under the tongue and with your mouth closed hold the thermometer in place until a reading is taken.
Wait at least 15-30 minutes after eating or drinking hot/cold substances before taking an oral temperature.
Rectal thermometer:
This is the most accurate type of thermometer, but it is not recommended for adults. Insert the probe gently into the rectum until the device beeps or the specified time elapses.
Use a water-soluble lubricant (such as KY-Jelly).
Axillary (armpit) thermometer:
This is a good option for children and babies. Place the thermometer under the armpit and hold the arm snugly against the body for the recommended time until the thermometer beeps.
Keep the area as dry as possible when taking a measurement.
Tympanic (ear) thermometer:
This is a quick and easy way to measure your temperature. Place the thermometer in the ear, click the button and hold it in place until it beeps.
Pulling the ear gently can help straighten the ear canal and ensure a snug fit for an accurate reading.
Infrared (forehead) thermometer:
This method is quick, non-invasive and suitable for children and adults. It is also useful when many measurements need to be taken quickly (e.g. in a screening setting). However, it may be less accurate than other forms of measurement. Point the thermometer at the forehead, click the button and wait until a reading is taken.
Keep the forehead dry, free from sweat or hair for optimal results.
Tips for accurate temperature readings
1. Choose the right thermometer: different thermometers have specific uses, so choose the one most appropriate for the age group and situation.
2. Follow manufacturer instructions: always adhere to the instructions provided with the thermometer as each device may have slightly different specifications.
3. Rest before measurement: wait for at least 15 minutes after physical activity or consuming hot/cold substances before checking temperature.
4. Consistent method: sticking to one method for consistency can help to monitor trends in body temperature over time.
What is considered a fever?
Fever: A body temperature of 38°C (100.4°F) or higher is indicative of a fever.
Low-Grade Fever: some sources might use the term "low-grade fever" for temperatures slightly above the normal range but below 38°C (100.4°F).
What is considered hypothermia?
Hypothermia is when the body temperature drops dangerously low, to below 35°C (95°F).
Summary
It is important to be aware that the method of measurement can affect the recorded temperature to a degree (not literally!). For example, oral, rectal, ear, and forehead temperature measurements may yield slightly different readings, however the cut-off ranges above for fever and hypothermia hold true.
It can be helpful to be familiar with your own baseline temperature and recognize any significant deviations from your normal range.