Fever & taking a temperature

What counts as a fever

• 38.0 °C (100.4 °F) or higher is a fever. In a baby under 3 months, this is a “call the doctor now” number, not a wait-and-see number. Small babies cannot fight infections well and can get sick quickly.
• Normal range for a baby is roughly 36.4 to 37.5 °C measured under the arm, a little higher rectally. Every baby runs slightly differently. What matters is the trend and how baby behaves.

How to measure (do it right, trust the number)

• Most accurate for newborns: rectal. Use a digital thermometer with a dab of vaseline. This is the number doctors mean when they say 38.0 °C.
• Easiest everyday check: armpit. Hold the arm gently against the body until it beeps. Fine for screening, confirm rectally if it reads high.
• Skip for now: forehead strips (inaccurate) and ear thermometers (too big for tiny ear canals under about 6 months).
• Measure when baby is calm. Right after crying, feeding, or being bundled up, readings run high. Unbundle, wait 10 to 15 minutes, measure again.

A warm baby is not always a fever

• Too many layers, a hot room, or a car seat can push temperature up. Rule of thumb: baby needs one more layer than you. Check the neck or chest, not the hands and feet, which always run cool.
• If baby feels hot: remove a layer, cool the room, offer a feed, then re-measure after 15 minutes. If it is still 38.0 °C or higher, call.

While you wait for advice

• Keep baby lightly dressed in a comfortable, not-cold room.
• Offer feeds often, fluids matter most.
• Do not cold-sponge, do not aim a fan at baby, and do not bundle up a shivering baby.