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HealthInfo Canterbury

Overview of fever (high temperature) in children

Important

If your baby with fever is under 3 months old, you should always see a doctor.

Phone 111 for urgent medical help if your child:

  • has blue lips and tongue
  • has severe difficulty speaking
  • has irregular breathing or stops breathing
  • has a worrying rash, especially one that doesn't go
    away when you press on it
  • is unconscious or you can't wake them up properly.

Child with a fever sleeping Fevers are common in children. Fever by itself does not tell you whether your child is seriously sick. Even an ordinary cold can cause a high fever.

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

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

The number on the thermometer can't tell you:

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

Other causes of high body temperature include:

Fever is a normal way for a child 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 child feel unhappy or uncomfortable, but the high temperature is very unlikely to cause any long-term problems.

Some 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.

When to see a doctor

If you are worried about your child, whether or not there is a fever, you should take them to see a doctor.

If your child has already seen a doctor but they are getting worse, go back to your doctor.

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

See a doctor urgently if your child with a fever:

  • is under 3 months old
  • looks unwell and you are 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, has 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
  • is not 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 is not fresh
  • is in severe pain
  • is not interested in surroundings (lethargic).

See a doctor if your child with a fever:

  • has a sore throat or joint pains
  • is drinking less than half of their normal breast milk or other fluid
  • is having fewer than four wet nappies in 24 hours
  • 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
  • is not improving after two days
  • has had a fever for more than five days.

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Adapted from KidsHealth NZ by HealthInfo clinical advisers. Last reviewed April 2020.

Page reference: 734318

Review key: HIFEC-49206