Taking a temperature
Under 3 months, 38 °C is an emergency
About 5 min Essential
Why it matters
In a newborn, fever can be the only sign of a serious infection. For a baby under 3 months, 38 °C (100.4 °F) or higher is always urgent: call a doctor or go to emergency care without waiting.
What you need
- A digital thermometer (not a glass mercury one)
- Petroleum jelly for a rectal reading
- Your phone to note the result
Step by step
- 1 Use a digital thermometer. Ear thermometers aren't reliable under 6 months.
- 2 Underarm: place the tip high in the armpit, hold the arm against their side and wait for the beep.
- 3 Rectal (the most accurate method under 3 months): lubricate the tip with petroleum jelly; lay your baby on their back with knees bent toward the tummy.
- 4 Insert the tip only about 1-1.5 cm (1/2 in), without pushing against resistance; hold your baby still and wait for the beep.
- 5 Write down the reading and the time. 38 °C (100.4 °F) or higher is a fever.
- 6 If your baby is under 3 months and at 38 °C or higher, call your doctor or emergency care right away. Give no medicine without asking a doctor.
- 7 At 3-6 months, 39 °C (102.2 °F) or higher is also a reason to call. Clean the thermometer with soap and water after use.
Common mistakes
- Using a glass mercury thermometer.
- Sponging with cold water or alcohol to bring the fever down.
- Giving fever medicine to a baby under 3 months without asking a doctor.
- Bundling up a feverish baby and trapping the heat.
When to see a doctor
- Under 3 months, 38 °C or higher: emergency.
- 3-6 months, 39 °C or higher.
- Fever with a seizure, blue lips, trouble breathing, a rash that doesn't fade when pressed, or hard to wake: call 112 right away.
- Their body feels cold and they are floppy and not feeding.
This guide gives general information and doesn't replace a medical exam. If you're worried about your baby, talk to your doctor.