Fever in Children: What Parents Should Know

Your child is burning up, cranky, and refusing to eat. The thermometer reads 39.1 °C. You're wondering: How serious is this — and what do I need to do right now?

The most important thing to know: fever is a natural protective response, not an enemy. The crucial question isn't how high the fever is — it's how your child is coping with it. In most cases, fluids, rest, and observation are enough. You'll find out exactly when you need to act below.

What Is Fever, Actually?

Fever is not a disease — it's a natural defence mechanism. The immune system raises the body's temperature to make it harder for viruses and bacteria to multiply. A healthy child's normal body temperature sits between 36.5 and 37.5 °C and varies over the day — in the evening it's usually about 0.5 °C higher than in the morning. In children, a high temperature is 38°C or above (NHS). In babies under 3 months, a temperature of 38°C or above needs urgent medical advice — contact a GP or call NHS 111 straight away (call 999 or go to A&E if your baby seems seriously unwell).

Those numbers are the NHS ones. Its page on high temperature (fever) in children (last reviewed 3 January 2024) says "A high temperature is 38C or more", that "the temperature usually returns to normal within 1 to 4 days", and explains what the temperature is for:

"A high temperature is the body's natural response to fighting infections like coughs and colds."

The good news: the body is working. Fever itself doesn't harm otherwise healthy children. What matters most is how the child behaves overall — a child with 39.5 °C who drinks and plays between episodes is far less concerning than a listless, apathetic child with only 38.5 °C.

How Do You Measure Fever Most Accurately?

Use a digital thermometer in the armpit — that is the method NHS guidance describes for children. Place it inside the top of the armpit, gently close the arm over it and keep it pressed to the side of the body. Leave it in for as long as the instruction leaflet says.

The NHS instructions are deliberately plain: "Place the thermometer inside the top of the armpit. Gently close the arm over the thermometer and keep it pressed to the side of the body. Leave the thermometer in place for as long as it says in the instruction leaflet."

• Buy a digital thermometer from a pharmacy or supermarket — it is the type the NHS points parents to
• Position matters: inside the top of the armpit, arm closed over it, held against the body
• Timing matters: some digital thermometers beep when they are ready; otherwise follow the leaflet
• Wait a few minutes before measuring if your child has just had a bath or been wrapped in a blanket — both can push the reading up temporarily

What matters more than the second decimal place is measuring the same way every time. Only then are last night's reading and this morning's actually comparable — and that trend is what your GP will ask about, not the single highest number you remember.

When Does Fever in Children Become Critical?

Your child's age is the most important factor. Infants under 3 months need immediate medical attention for any temperature at or above 38°C — their immune systems are still immature and bacterial infections can worsen extremely fast. Older children follow different thresholds. The values in the table aren't where fever begins — they mark when to seek medical advice.

Age	Contact a doctor from	Recommendation
0–3 months	from 38°C	See a GP / call NHS 111 straight away — urgent; 999 / A&E if seriously unwell
3–6 months	from 39°C	Call NHS 111 or see a GP
6+ months	from 39°C	See your GP if other symptoms or persistent fever; otherwise monitor

What Helps with Fever — Home Remedies and Medication?

Most children with a high temperature don't need medication — what they need most is plenty of fluids, light clothing, and rest. NHS advice is not to try to cool a child down deliberately: no undressing, no sponging. Medication helps when the child is visibly distressed, but only brings the temperature down temporarily.

Home Remedies

• Plenty of fluids: Water, tea, or diluted juice — fever dehydrates the body
• Light clothing: Don't bundle up too warmly so the body can release heat
• Check on them regularly: including during the night — how your child seems matters more than the reading
• Rest: The body needs energy to fight — quiet activities are fine

Medication

• Paracetamol (e.g., as syrup or suppository): from 2 to 3 months, if your baby weighs over 4kg and was born after 37 weeks
• Ibuprofen: from 3 months, if your child weighs more than 5kg
• Never give aspirin to children under 16 (risk of Reye's syndrome)

The NHS sets the dose by age band rather than by a weight calculation — look your child's age up on the pack, and check the strength printed on the bottle. When in doubt, ask your GP or pharmacist.

When Do You Absolutely Need to See a Doctor?

Some warning signs require immediate medical attention — regardless of how high the fever is. Call 999 or go to A&E immediately for: a febrile seizure, stiff neck, breathing difficulties, a rash that doesn't fade under pressure, loss of consciousness, or bluish lips.

In babies under 3 months, a temperature of 38°C or above needs urgent medical advice — contact a GP or call NHS 111 straight away (call 999 or go to A&E if your baby seems seriously unwell).

The NHS list of do's and don'ts (reviewed January 2024) is short and worth knowing by heart. Give plenty of fluids, and food if they want it. Check on your child regularly, including during the night. Keep them at home. Give paracetamol or ibuprofen if they are distressed or uncomfortable — and never aspirin to a child under 16.

See your GP soon (not an emergency, but don't delay):

• Fever lasting 5 days or more without improvement
• Child barely drinking or showing signs of dehydration
• Fever returns after a quieter period
• Severe ear pain or throat pain

How Do You Document the Progression Correctly?

When fever lasts several days, good documentation is crucial — it helps you recognise patterns and is invaluable at the doctor's office. At each measurement, record: time, temperature, measurement method, any medications given (drug name, dose, time), and how the child is generally doing.

What a record can do also stops somewhere clear: it describes, it does not diagnose. Which illness is behind the temperature, and whether it needs treating, is a decision for your GP — diagnosis and treatment belong with a clinician, not with a guide like this one.

With Mona, you can do this quickly even at 3 AM — the app shows you the fever trend as a chart and automatically reminds you about medication times, so no dose gets forgotten or accidentally doubled.

Frequently Asked Questions About Fever in Children

At What Temperature Does a Child Have a Fever?

In children, a high temperature is 38°C or above (NHS). Measure with a digital thermometer in the armpit; NHS guidance gives no correction factor to add on top. In babies under 3 months, 38°C or above needs urgent advice — contact a GP or call NHS 111 straight away.

Should I Reduce the Fever or Let It Run?

The child's level of discomfort — not the fever itself — is the deciding factor. If your child is drinking, sleeping, and responsive despite the fever, you don't need to give medication. If they're clearly suffering (headache, body aches, severe restlessness), paracetamol or ibuprofen can help — always dosed strictly by body weight.

How Long Does Fever Last with a Normal Infection?

Most viral infections cause fever for 2–4 days, then it gradually subsides. If the fever lasts 5 days or more or rises again after a quieter phase, your GP should examine the child — this can indicate a secondary bacterial infection.

Should I Try to Cool My Child Down?

No. NHS advice is explicit: "do not undress your child or sponge them down to cool them", and equally "do not cover them up in too many clothes or bedclothes". A high temperature is the body's response to an infection, not something to be argued down with cold water. Fluids, light clothing and regular checks are the whole list.

When Can My Child Go Back to Nursery?

The general rule: 24 hours fever-free without fever-reducing medication — only then is the child typically ready for nursery or childminder again. For certain infections (such as scarlet fever, hand-foot-mouth disease), longer exclusion periods apply. When in doubt, check with your GP.

What Should I Do If the Fever Spikes Above 40 °C at Night?

Stay calm — 40°C is uncomfortable, but not an automatic emergency for otherwise healthy children over 3 months. Check the warning signs above (neck, breathing, consciousness, skin rash). If none apply: offer plenty of fluids, dress lightly, give fever medication if needed, and monitor. If your child seems very unwell or their condition worsens, call NHS 111 or 999 — what matters is how unwell your child seems, not the exact number.

Summary: Wait, See a Doctor, or Emergency?

Situation	What to do
Infant under 3 months with fever from 38°C	Urgent — NHS 111 / GP straight away (999 if seriously unwell)
Febrile seizure, breathing difficulty, stiff neck, unresponsive	Call 999
Rash that doesn't fade under pressure	Call 999
Fever 5 days or more, barely drinking, or your child seems very unwell	GP today or NHS 111
Ear pain, throat pain, fever returning after improvement	GP soon
Child drinks, is responsive, no warning signs	Monitor, fluids, rest