How to take a temperature
Updated: October 2026
The number only helps if you know the site and the wait. This is how to take a temperature the way the NHS describes it at home: armpit for a child under five, mouth for an adult with a digital stick, then the call list rather than the colour on the screen. The NHS says the armpit wait is usually about 15 seconds, or the leaflet time. Sticks in the 15 October 2026 listings say 8, 10, 30, or 60 seconds. Models are on the [thermometer comparison](/hub/climate-measuring/thermometer). Products Compared did not lab-test them. A purchase can earn a commission at no extra cost to you.
The number only helps if you know the site and the wait.
The number only helps if you know the site and the wait. This is how to take a temperature the way the NHS describes it at home: armpit for a child under five, mouth for an adult with a digital stick, then the call list rather than the colour on the screen. The NHS says the armpit wait is usually about 15 seconds, or the leaflet time. Sticks in the 15 October 2026 listings say 8, 10, 30, or 60 seconds. Models are on the thermometer comparison. Products Compared did not lab-test them. A purchase can earn a commission at no extra cost to you.
Our top picks
| Badge | Product | Listed time | Sites | Cell | Note | Price | Offer |
|---|---|---|---|---|---|---|---|
| Best overall |  Braun Braun Age Precision PRT2000 | 8 s after an age step | Oral, rectal, underarm | Lithium included; screen dark for age | 9.2 | about £10 | View offer |
| Best value |  femometer femometer DMT-2032 | 10 s or 60 s | Oral, rectal, underarm | C cell included | 9.2 | about £6.99 | View offer |
| Alternative |  Berrcom Berrcom digital stick | 30 s on the attribute | Oral, armpit, rectal | Count not stated; often arrived flat | 9.0 | about £5.99 | View offer |
On this page
Take a child’s temperature in the armpit
For a baby or a child under five, the NHS baby-temperature page uses three steps. Sit the child on your knee. Put a digital thermometer in the armpit. Hold the arm gently but firmly against the body for the time in the instructions, usually about 15 seconds. Some units beep. Then read the display. That page rejects glass mercury thermometers. Ear thermometers and forehead strips are a different method.
The beep is the end of the wait, not a diagnosis. If the leaflet and the NHS line of usually about 15 seconds disagree, follow the leaflet and still use the NHS call list. The Braun PRT2000 lists 8 seconds after an age step on a screen reviews say stays dark. The femometer DMT-2032 says 10 seconds in the bullets and 60 in the attribute table. The Berrcom lists 30 seconds. One review said about 3 minutes and no beep, and many cells arrived flat. A flat cell is a failed reading, not a low temperature. Which stick to buy is on the thermometer buying guide.
What the number means, and when to call
On the NHS fever-in-children page, 38 °C or more is the line it uses for a fever. The same page says to wait a few minutes and try again if the child has just had a bath or been wrapped in a blanket. Age changes the call, before any product name matters.
Call 999 if a baby under 3 months has a temperature of 38 °C or higher, or a baby aged 3 to 6 months has a temperature of 39 °C or higher. The fever-in-children page names those same temperatures and says call 111. If both pages are open, follow 999 for those ages. Also call 999 for a rash that does not fade when you press a glass on it, a stiff neck, a first fit, difficulty breathing, an unusual colour, or a child who is hard to wake. A temperature under 36 °C in a baby or young child is on that urgent-help page as well.
Call 111 if the fever has lasted 5 days or more, if the child is not themselves, or if you are worried about feeding. Do not use 111 online for a child under five. That service is for people aged 5 and over. A red screen is the manufacturer’s band, not either of those calls.
Adults at home
For an adult, the method is oral and digital: clean the tip, place it under the tongue towards the back, close the lips, and wait for the beep. Feeling hot or shivery still matters when the number is under 38 °C.
That page says not to use glass, an infrared thermometer, because some do not meet UK regulations, or a forehead strip. An ear thermometer means following the leaflet, usually pulling the ear up and back. A hospital band such as 36.8 °C to 37.2 °C for a newborn is not the home rule for a child on the sofa. This page does not give medicine doses. Ask a pharmacist or a clinician if you are unsure what to give.
If the second reading is different
Two readings often disagree. One Braun stick review lists 37.8 °C, then 37.3 °C, then 36.8 °C in the armpit. If the child has just had a bath or been wrapped up, wait a few minutes and try again in the same armpit.
A flat cell, a unit that never beeps, or a dark screen during the age step will not give a number you can compare. Ear and forehead are a different site. A gap against the armpit is not proof the stick is broken. If the red-flag list is already true, call.
Common questions
How long do I hold the thermometer in the armpit?
Hold it for the time in the instructions. The NHS says that is usually about 15 seconds, and that some thermometers beep when they are ready. The sticks in the table list 8 seconds, both 10 and 60 seconds, or 30 seconds. One Berrcom review described about 3 minutes and no beep. A flat cell is not a finished reading.
What temperature counts as a fever?
The NHS pages on fever in children and in adults use 38 °C or more. For an adult, feeling hot or shivery still counts when the display is lower. For a baby or young child, a temperature under 36 °C is on the NHS urgent-help page as a reason to get help. Wait a few minutes after a bath or a blanket before you treat one number as the temperature.
When do I call 111, and when do I call 999?
Call 999 for a baby under 3 months at 38 °C or higher, or a baby aged 3 to 6 months at 39 °C or higher. The fever page says call 111 for those same temperatures, so follow 999 when they differ. Call 111 for a fever of 5 days or more.
Can I use 111 online for a toddler?
No. 111 online is for people aged 5 and over. For a child under five, call 111. If the urgent symptoms above are present, call 999. A colour on the screen does not choose the service.
How do adults take a temperature, and why does the NHS warn against infrared?
Clean a digital tip, place it under the tongue towards the back, close the lips, and wait for the beep. The NHS adult fever page says not to use glass, infrared thermometers, or forehead strips, because some infrared units do not meet UK regulations. An ear thermometer belongs in that method only if you follow its leaflet. A reading under 38 °C does not cancel feeling hot or shivery.
Related pages
Sources
Public UK sources used for this comparison. Listing prices are from amazon.co.uk on 15 October 2026.
- NHS — how to take your baby's temperature (retrieved 15 October 2026)
- NHS — fever in children (retrieved 15 October 2026)
- NHS — fever in adults (retrieved 15 October 2026)
- NICE NG143 — fever in under 5s (retrieved 15 October 2026)
- MHRA — infrared thermometers, caution in use (retrieved 15 October 2026)
- MHRA — temperature screening equipment (retrieved 15 October 2026)
- GOV.UK — chill, freeze and defrost food safely (retrieved 15 October 2026)
- Food Standards Agency — cooking your food (retrieved 15 October 2026)
- RHS — heating greenhouses efficiently (retrieved 15 October 2026)