HealthInfo Canterbury

Overview of fever (high temperature) in children

Fevers are common in tamariki (children). A fever by itself doesn't tell you if they're seriously sick. Even an ordinary cold can cause a high fever.

Your child's normal body temperature is around 37°C. Your tamaiti child has a mild fever if their temperature is higher than 38°C. A high fever usually means more than 39°C.

If your tamaiti is miserable, seems unwell and feels hot, you can use a thermometer to take their temperature. You don't need to do this if they seem well.

The number on the thermometer can't tell you:

• what's causing the fever
• how sick they are.

The most common cause of a fever in a tamaiti is a viral infection. A bacterial infection is a less common but more serious cause.

Other causes of high body temperature include:

• immunisation – this usually only causes a mild fever
• wrapping a pēpi baby in too many warm layers of clothing or bedding.

Fever is a normal way for a tamaiti to fight an infection. The body's natural reaction to infection with a virus or bacteria is to raise the temperature inside the body. This helps to kill the infection.

Being hot may make your tamaiti feel unhappy or uncomfortable, but the high temperature is very unlikely to cause any long-term problems.

Some tamariki children have convulsions (called febrile convulsions) when they have fevers. These look very worrying, but even these febrile seizures are very unlikely to cause long-term problems.

Getting help for your child with a fever

If you're worried about your tamaiti, whether or not there's a fever, you should take them to see a doctor.

If they've already seen a doctor but they're getting worse, go back to your doctor.

Tell your doctor if your tamaiti has been overseas in the last few weeks or has been around someone who is unwell.

See a doctor urgently if the tamaiti with a fever:

is under 3 months old looks unwell and you're concerned is very pale or feels cold to touch is floppy, sleepy or drowsy is becoming less responsive has an unusual high-pitched cry has trouble breathing, noisy breathing or is breathing fast complains of a stiff neck or light hurting their eyes has a severe headache

refuses to drink, even small sips isn't doing wee vomits a lot and can't keep sips of replacement drinks down vomits green fluid (bile) vomits blood – this may be red or brown or look like coffee grounds if it isn't fresh is in severe pain isn't interested in surroundings (lethargic).

See a doctor if the tamaiti with a fever:

has a sore throat or joint pains is drinking less than half their normal breast milk or other fluid is having fewer than four wet nappies in 24 hours has vomited half or more of their feed for the last three feeds

has frequent and watery poo (diarrhoea) complains or cries when doing wee is in pain is getting sicker isn't improving after two days has had a fever for more than five days.

  HealthInfo recommends the following pages

• KidsHealth:
  • Thermometers – How to use them

    Easy-to-follow instructions on the different kinds of thermometers and how to use them.

  • What is a fever?

    What causes a fever and how to treat it.

• Ministry of Health – Child sickness danger signals

  This two-page handout explains what danger signals to watch for when your tamaiti is sick.

On the next page: Helping your child with fever (high temperature)

Content shared between HealthInfo Canterbury, KidsHealth and Health Navigator NZ as part of a National Health Content Hub collaborative. Last reviewed November 2021.

Page reference: 734318

Review key: HIFEC-49206