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26 Sep 2020

Digital thermometers: what type to buy and how to take your temperature correctly

Need a way to check if you have a fever or potential COVID-19? We explain the pros and cons of different types of thermometer, where you can buy one and how to take your temperature accurately

As we head into autumn, children go back to school and the season of coughs and sneezes begins, a thermometer is a useful piece of kit to have to hand to keep tabs on your health.

If you're looking to buy a thermometer, we've rounded up our expert tips on choosing the best type, 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.

Types of thermometer: which is best?

If you're shopping for a thermometer, you'll find yourself having to decide between various types.

The cheapest is a basic digital thermometer that you hold under your tongue or underarm, but you can also get versions that take in-ear readings or no-contact options you point at your forehead, but these tend to be more expensive.

Strip thermometers aren't considered to be very accurate and the old mercury versions are also best consigned to history.

Here's a quick run down of the pros and cons of the different types:

Digital thermometers (typically £5 to £10)

These are 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 take care to clean it between uses.

You need to follow the instructions carefully, too - usually they involve not having had a hot or cold drink or food for 30 minutes before taking your temperature, or having 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 you end up breaking it accidentally.

Digital in-ear thermometers (typically £20 to £40)

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

You may get an inaccurate reading if the device isn't positioned correctly in the ear or if there's a build up of earwax.

They're 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 aren't 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 (typically £30 to £70)

As the name suggests, with no-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.

Non-contact thermometers tend to be more expensive, 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.

Take your temperature using a smartphone

You can get a small plug-in device that, when hooked up to your smartphone via the headphone jack, turns 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. You can also see all our digital thermometer reviews.

What not to buy: forehead strip thermometers

These are appealingly cheap at £10 or less and have some novelty value. You place them on your forehead and the strip changes colour to indicate temperature.

They're cheap, but 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.

Buying a thermometer: who has stock?

Digital thermometers are one of the items that have been a victim of increased demand as the COVID-19 pandemic gathers pace.

Back in March it was pretty hard to track one down, and they are in demand again. We had a quick check of major retailers and places such as Argos, Boots and Superdrug do have stock, but you may have a more limited selection than normal - the cheaper options, in particular, tend to sell out fast.

Try asking at your local pharmacy as they may have stock or be able to tell you when stock is coming in.

How to tell if you have a fever without a thermometer

Don't panic if you can't track down a thermometer. If you 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, achey and generally unwell is a sign of fever.

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.

As different thermometers work in different ways, and getting it right affects the accuracy of the reading, 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.

  1. Tips for getting the best reading:

Fever aside, there are other factors that could affect the reading you get from a thermometer.

It's worth checking it when you feel well, so you have an idea of what's normal for you, as it can vary slightly.

If you're checking your temperature multiple times a day to track 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 effect.

What is considered a 'high' temperature?

According to official NHS guidance, a 'high' temperature is considered as 38°C or over.

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

Anybody can suffer from a fever, regardless of age. If you think you have a fever the best ways to help yourself recover are:

Be careful not to use flu remedies if you're taking paracetamol and ibuprofen tablets as they usually contain these drugs, too, so it's easy to take more than the recommended dose.

If you or someone in your family has a fever and you need advice, you can call NHS 111 or your GP.

Coronavirus symptoms

COVID-19 affects the lungs and airways, and a fever and new cough are some of the key symptoms. Government advice is to stay at home if you show either of the following symptoms:

If you think you might have these symptoms, your first port of call should be the NHS 111 online COVID-19 tool.

This story was originally published on 26 March 2020, but updated 25 September 2020.