How to take a child's temperature and how to log it
The same thermometer in three places gives three different numbers. Pick the method that fits the age, stick with it and log the result together with the method. Then the trend means something.
Last updated: 29 September 2026
Which method at which age (NICE NG143)
| Age | Method recommended by NICE |
|---|---|
| under 4 weeks | electronic thermometer in the armpit |
| 4 weeks to 5 years | electronic or chemical dot thermometer in the armpit, or an infra-red ear thermometer |
| 0-5 years | NICE: do not routinely measure in the mouth or the rectum |
| older children | armpit, ear; in the mouth once the child can hold the thermometer under the tongue |
No-touch forehead thermometers are handy for a quick check, but NICE does not recommend them for measuring in young children. The American Academy of Pediatrics considers rectal measurement the most accurate in babies. If you measure that way, always do it the same way and log the method. Different methods give different numbers: do not convert them, compare readings taken the same way.
Technique
- Armpit: dry skin, tip in the middle of the armpit, arm pressed down, full time from the thermometer's instructions.
- Ear: pull the ear gently back (down in babies), aim along the canal, measure twice and take the higher.
- Forehead: dry forehead, no hat for 10 minutes, indoors.
How often
For a common infection 2-3 times a day and whenever the child looks worse. Do not wake a sleeping child to measure. Whether the temperature drops after a medicine does not tell you how serious the illness is (NICE); how your child looks matters more.
How to log it so the doctor can use it
- time and reading with the method (38.4 °C armpit),
- every dose: which product, how many ml, when,
- symptoms besides fever: cough, vomiting, rash, how much they drank, how often they passed urine.
Such a list shows at a glance how long the fever has lasted. More than 3 days is a reason to see a doctor.
These numbers are conversions from leaflets and guidelines. Before giving a medicine, confirm them at the source:
- NHS: paracetamol for children · NHS: ibuprofen for children
- NICE NG143: fever in under 5s · AAP HealthyChildren.org
- Polish medicines register (URPL): official leaflets of the products listed here
- Your own country's medicines regulator and the leaflet in the box always take precedence.
Tired of keeping track on a scrap of paper?
Oh Fever records what you gave and when. Free for one child.
Shows the time since the last dose, the doses recorded in 24 hours and the leaflet tables and sentences word for word, with a link to the official leaflet. It does not calculate or suggest doses.
Download on the App StoreAlso shows the row of the leaflet table for your child's weight and age, counts down to the next dose the leaflet allows and warns before the daily limit is crossed.
Get it on Google PlayRead next
NICE NG143: Fever in under 5s
AAP: How to take a child's temperature
This content is for information only and does not replace your doctor or the medicine leaflet. Oh Fever and this website are not a medical device. Doses on this page come from the dosing tables in the leaflets of products registered in Poland, converted to millilitres and rounded to the syringe marks, never above the table. Check the strength on the package before giving any medicine. For high fever, any fever in an infant under 3 months, or worrying symptoms, contact a doctor.