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14 September 2021

Digital thermometers: what type to buy and how to use

We explain the pros and cons of different types of digital thermometer, where to buy them and how to take your temperature accurately
Anna Studman

A digital thermometer can be a useful tool to check your health at home. We've rounded up our expert tips on choosing the best type of digital thermometer for your needs, typical prices and how to use them properly.

The advice on this page is primarily aimed at adults wishing to take their own temperature. If you’re looking for advice on taking the temperature of babies or young children, see our guidance on how to take a baby or child's temperature.

The cheapest type of thermometer is a basic digital thermometer that you hold under your tongue or underarm. 

You can also get versions that take in-ear readings, or no-contact options that you point at your forehead – these tend to be more expensive. 

Other types have fallen out of favour: strip thermometers aren’t considered to be accurate, and the old mercury versions are best consigned to history for safety reasons.

If you don't have a thermometer and think you might have a fever, the NHS suggests checking if the skin on your chest and back is hot to touch. This, along with feeling shivery, achy and generally unwell, is a sign of fever.

See our digital thermometer reviews to discover which models performed best in our tests. 

Types of thermometer

Find out about the pros, cons and average price range of different types of thermometer below. 

Digital thermometers

Typical price: £5-10

This is the most common type of thermometer, and a good basic option. They should produce accurate readings when used correctly. 

You can place the thermometer under your armpit, but you’ll get a more accurate reading from the mouth, where it should sit under the tongue. 

The only real disadvantage is that it can be a bit uncomfortable to sit with it under your tongue for several minutes, and you’ll need to clean it between uses. 

You need to follow the instructions carefully, too – usually they say you shouldn't have had a hot or cold drink or food for 30 minutes before taking your temperature, or have just come in from outside or done exercise, which can be quite restrictive.

Try to steer clear of old-style mercury thermometers – mercury is toxic and will be a pain to clean up if the thermometer gets broken.

Digital in-ear thermometers

Typical price: £20-40

Ear thermometers are quick and easy to use, taking just a few seconds to get a reading. They use infrared technology to measure the temperature inside your ear. 

You might get an inaccurate reading if the device isn’t positioned correctly in the ear, or if there’s a build-up of earwax. 

In-ear models are pricier than digital thermometers, but might be a better option if you want a quick solution, or are trying to take the temperature of a child who doesn’t like to sit still for long. They're not recommended for newborns, though.

Some use disposable probe covers, which are convenient but an ongoing cost. Otherwise you’ll need to clean the ear probe between uses.

Non-contact thermometers

Typical price: £30-70

As the name suggests, with non-contact thermometers you don’t need to press the device against your skin or place it in your mouth. 

These thermometers use infrared technology to detect heat coming from the surface of your skin, and are usually quick to give a reading.

Non-contact thermometers tend to be more expensive than other types, but if you’re looking for a non-invasive way to check a temperature and want to avoid the faff of cleaning the thermometer between uses, they can be a good option.

Taking your temperature using a smartphone

There are now small plug-in devices available which, when hooked up to your smartphone via the headphone jack, turn it into a digital infrared thermometer. 

To record a temperature, you simply place the gadget on your forehead or in your ear. Readings taken from the thermometer are fed into the smartphone app, which stores results so you can track changes over time. 

See the Oblumi Tapp smartphone thermometer first look review for our first impressions.

Strip thermometers

We recommend avoiding these. They're appealingly low priced, at £10 or less, and have some novelty value. You place them on your forehead and the strip changes colour to indicate the temperature. 

However, the NHS doesn’t recommend them as they measure the temperature of your skin, rather than your body.

You’re better off using a digital thermometer to get an accurate reading from the armpit or mouth.

Where to buy digital thermometers

Most pharmacies and stores such as Boots and Superdrug will stock a range of thermometers. 

Generalist retailers such as Argos, John Lewis, Currys and supermarkets also stock them. If buying online, take care to buy from reputable brands or retailers.

How to take your temperature

Whatever type of thermometer you end up using, make sure you’ve cleaned it properly according to the instructions. This is usually done with cool, soapy water, but if you’re using an ear thermometer you need to use a dry cloth. 

Different thermometers work in different ways, and getting it right affects the accuracy of the reading, so it’s really important to always start by reading the manufacturers’ instructions – even if you’ve had a similar thermometer before. 

If you have any further questions, consider asking a pharmacist.

Getting the best reading

Fever aside, there are other factors that could affect the reading you get from a thermometer. It’s worth checking your temperature when you feel well, so you have an idea of what’s normal for you, as this can vary slightly between individuals. 

If you’re checking your temperature multiple times a day to track the progress of a fever, try to keep the conditions consistent. For example, excess clothing, bedding, having eaten or drunk recently, or outside weather conditions can all have an impact.

What is considered a 'high' temperature?

According to official NHS guidance, a ‘high’ temperature is considered as 38°C or more.

What is a fever?

According to the NHS, a fever is actually a process by which your body fights infections. It stimulates your immune system: your body’s natural defence. A fever makes it harder for the bacteria and viruses that cause infections to survive by increasing your body temperature.

How to treat a fever at home

If you think you have a fever, these are the best ways to help yourself recover:

  • Drink plenty of fluids Drinking water regularly is key to treating a fever. Try to avoid alcohol, tea and coffee.
  • Rest up Stay in bed if you can. You might want to take paracetamol in appropriate doses to deal with aches and pains.
  • Stay cool Removing extra layers of clothing can help to bring your temperature down.

Which painkillers are best? Find out what works best for different ailments, from tackling pain to dealing with fever.

Fever as a symptom of Covid

A fever is one of the key symptoms of Covid, but isn't always present with a Covid infection. Even if you get a normal reading on your thermometer, pay attention to other symptoms and act accordingly. 

If you've got a fever or other symptoms including a new, continuous cough or a loss of taste and smell, government advice is to take a PCR test and then self-isolate while you wait for the result. From there, you should follow government advice on how long to self isolate depending on what your result is.