A high temperature, also known as a fever, is usually a symptom of a medical condition, such as an infection or inflammation in the body.
A person is said to have a fever if their temperature is 38C or higher.
Taking your temperature is the best way to tell if you (or someone else) have a fever. To do so, you will need a thermometer.
What are the different types of thermometer?
There are several types of thermometers. These can be bought from a pharmacy, and include:
- digital thermometers - these are accurate and easy to use. You can use them to take a person’s temperature from their armpit or mouth
- ear thermometers - these are also easy to use, but you must place the thermometer correctly in the ear for an accurate reading
- strip-type thermometers - these strips are applied to the skin and take the temperature of the skin rather than the body. This means that they are not very accurate
- mercury-in-glass thermometers - these old-fashioned thermometers are no longer available to buy. If you do have access to one, do not use it. Mercury-in-glass thermometers contain the highly-poisonous substance mercury, which may be released if the thermometer is dropped and breaks
How to take a person's temperature
To take a person’s temperature, you should begin by cleaning the thermometer. Read the manufacturer's instructions because different thermometers work differently.
In general, you should place a digital thermometer in the person’s mouth or under their armpit. An ear thermometer should be firmly placed in the ear.
Before taking a person’s temperature, make sure they are not doing or wearing anything that may make them unnaturally hot and raise their temperature. This means they should not have their temperature taken:
- after having a warm bath
- while wrapped up tightly in a blanket
- while in a very warm room
- while wearing lots of layers of clothes
- after being very active
- while holding a hot water bottle
When to worry about a person’s temperature
Contact a doctor immediately if you or someone else has a temperature of 38C or higher and:
- they have a fit
- they are becoming more unwell
- they have swelling, redness or pain around a cut or wound
- they have a rash that does not disappear when you press a glass on it
- they have a stiff neck, shortness of breath or chest pains
- they have not passed urine in the past 24 hours
- the fever has lasted longer than 5 days
- they have recently travelled abroad
- they have a weakened immune system (for example, they are taking immunosuppressive drugs or are having chemotherapy)
- they have a long-term condition, have had recent surgery or are pregnant
Find out when else you should seek medical attention for a fever.
How do I take someone's temperature? [Internet]. nhs.uk. 2020 [cited 20 March 2020]. Available here.
Knott D. Fever (High Temperature) [Internet]. Patient.info. 2020 [cited 20 March 2020]. Available here.