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How to take someone’s temperature

Medically reviewed

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.

References

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.

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Important: Our website provides useful information but is not a substitute for medical advice. You should always seek the advice of your doctor when making decisions about your health.

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