How to take a baby’s temperature
For babies under 3 months, a rectal reading is the most accurate. The armpit is the easiest but least accurate, so double-check a doubtful reading another way. A forehead (temporal artery) thermometer works from 3 months and an ear thermometer from 6 months.
Methods by age
| Method | From what age | Accuracy |
|---|---|---|
| Rectal | from birth | Most accurate, recommended under 3 months |
| Forehead (temporal artery) | from 3 months | Good, following the thermometer’s instructions |
| Ear | from 6 months | Good, less accurate in younger babies |
| Armpit | any age | Least accurate, fine as a first check |
How to take a rectal temperature safely
- Use a digital thermometer and put a little petroleum jelly on the tip.
- Lay your baby on their back with knees bent toward the tummy, or tummy down across your lap.
- Gently insert the tip about 1.5 cm (half an inch) and hold it until it beeps.
- Wash the thermometer with soap and water afterwards and do not use it in the mouth.
Armpit readings are lower
An armpit reading is usually lower than a rectal one. If the result is borderline, or your baby seems unwell despite a low reading, measure again with a more accurate method.
A fever is 38.0°C (100.4°F) or higher. In a baby under 3 months, any fever needs urgent medical attention. Thresholds for older children: baby fever: when to see a doctor.
Fever thresholds by age, when to call emergency services, the glass test and space for your pediatrician’s number. One A4 page to print. Download the cheat sheet
Calm Parent
Save readings with the time and the method, and the chart shows whether the temperature is rising or falling. No ads, 14 days of Premium free.
Get it on Google PlaySources
- American Academy of Pediatrics, How to Take a Child’s Temperature (healthychildren.org)
This article is for information only and does not replace medical advice. If something worries you, contact a doctor. In an emergency, call your local emergency number.