How to Take Your Child's Temperature Accurately
Armpit with a digital thermometer is the practical home method for babies, ear is quick and reliable from about 6 months, and forehead is convenient but can read low. The method matters as much as the number. Use the same method each time and tell the doctor which one you used.
The four methods compared
Each method has a place. The right one depends mostly on your child's age and what you already own. What matters most is using a method correctly and consistently.
Pull the ear back and slightly up, insert snugly, use the same ear each time. Wax or poor aim reads low. Not for babies under 6 months.
Fast and no contact discomfort, good for a first look. Most affected by sweat, technique, and room temperature. Confirm a borderline reading with another method.
Tip in the centre of a dry armpit, arm held against the body until it beeps. The practical home method for young babies. Reads slightly lower than core.
The clinical gold standard for infants but rarely needed at home. Only do this if a clinician has shown you how. Most parents do not need it.
Which method by age
- Under 3 months: armpit (axillary) with a digital thermometer is the practical choice. Any fever of 38.0°C or above at this age needs urgent assessment.
- 3 to 6 months: armpit is still reliable. Ear thermometers are not recommended until around 6 months because the canal is small.
- 6 months to 5 years: a well-taken ear reading is accurate and fast. Forehead is fine for a quick check, confirmed by ear if borderline.
- Over 5 years: ear or forehead both work. Older children can also manage an oral reading if you have a thermometer designed for it.
Getting an accurate reading
Whichever method you use, a few habits make readings more reliable:
- Wait if your child has just been crying, bathing, feeding, or bundled in blankets. Any of these can push a reading up or down. Give it 20 minutes.
- Use the same method and, for ear readings, the same ear each time, so you are comparing like with like.
- Follow the device instructions for placement. Most low readings come from placement, not a faulty thermometer.
- Check the batteries. A weak battery on an infrared device can give inconsistent readings.
- Track the trend across several readings rather than reacting to one number. A fever that is slowly settling tells you more than a single spike.
What counts as a fever
As a general guide, a temperature of 37.5°C or above is considered a fever, and 38.5°C or above is a high fever. Body temperature naturally varies through the day and rises a little in the evening, so a single reading just over 37.5°C in a well child is rarely a concern on its own.
Use the same numbers whatever thermometer you use. Do not add or subtract.
The exception is young babies. In a baby under 3 months:
- 37.5 to 37.9°C: remove a layer and recheck after 20 minutes. Get advice the same day if it stays there.
- 38.0°C or above: this is urgent. Get your baby assessed now, regardless of how they look.
Common measuring mistakes
- Taking a forehead reading straight after your child comes in from a warm or cold environment.
- An ear probe aimed at the canal wall rather than the eardrum, or blocked by wax, reading low.
- A loose armpit placement where the tip is not fully against skin.
- Re-measuring every few minutes and reacting to small swings instead of the overall trend.
- Switching methods between readings, then comparing numbers that were never measured the same way.
→ Fever in a baby under 3 months: what to do
→ Toddler fever 39°C: when to monitor vs seek help
When to get help now
Call 995 now if your child has a fever and any of these:
- !A seizure lasting more than 5 minutes (give rectal diazepam if a doctor has prescribed it, and still call)
- !Struggling to breathe (skin pulling in under the ribs, nostrils flaring, or grunting), pauses in breathing, or lips turning blue or grey
- !Cannot be woken, or floppy and not responding to you
- !A rash of small red or purple spots that does not fade when you press a glass on it
- !Swelling of the lips, tongue, or face, with any difficulty breathing
- !Cold, clammy, or mottled skin, with drowsiness or restlessness
Go to the nearest 24-hour A&E or children's emergency now if:
- !A baby under 3 months with a temperature of 38.0°C or above
- !A first febrile seizure, even if it has stopped
- !After a seizure: confused, still drowsy after 30 minutes, or more than one seizure in a day
- !A stiff neck, or crying in pain when bending the head forward
- !Unusually drowsy or hard to wake, but can be woken
- !Dengue warning signs as the fever comes down: tummy pain, repeated vomiting, bleeding gums or nose, or very tired
- !No urine or wet nappy for 12 hours or more
- !No tears when crying, sunken eyes, or a very dry mouth
- !Cannot keep any fluids down
- !Green vomit
- !A temperature above 40°C that is not coming down, and your child seems unwell
Frequently asked questions
Which way of taking a temperature is most accurate?+
Rectal readings are the gold standard for accuracy in babies but are rarely needed at home. Among everyday methods, a well-taken ear (tympanic) reading is the most accurate for children over 6 months. Forehead scanners are convenient but can read low if used incorrectly. Armpit readings are reliable enough for young babies when done carefully.
Are forehead thermometers accurate for children?+
Forehead (temporal or infrared) thermometers are quick and good for a first check, but they are the most affected by technique, sweat, and room temperature, and they tend to read slightly low. If a forehead reading shows a fever, or your child seems unwell despite a normal forehead reading, confirm with an ear or armpit measurement.
How do I take an accurate ear temperature?+
Gently pull the ear back and slightly up to straighten the canal, insert the probe snugly, and take the reading. Use the same ear each time. Ear wax or a probe that is not aimed at the eardrum can give a falsely low reading. Ear thermometers are not recommended for babies under 6 months because the canal is too small.
What is the best thermometer for a newborn?+
For babies under 3 months, a digital thermometer used under the arm (axillary) is the practical home choice. Place the tip in the centre of a dry armpit, hold the arm against the body, and wait for the beep. At this age, 38.0°C or above needs urgent assessment. For 37.5 to 37.9°C, remove a layer and recheck after 20 minutes. Get advice the same day if it stays there.
Do I need to add a degree to an armpit reading?+
Different methods read slightly differently, and armpit readings tend to be a little lower than core temperature. Rather than adding or subtracting, the practical approach is to use one method consistently, know what a normal reading looks like for your child on that method, and tell the doctor which method you used. Use the same fever numbers whatever thermometer you use.
How often should I check my child's temperature?+
Check when you have a reason to: your child feels hot, seems unwell, or you are watching how a fever responds to medicine. Constant re-checking tends to raise anxiety without changing what to do. Every few hours during an active fever is usually enough.