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).

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?

The most accurate method for young children is rectal measurement (in the bottom). Ear and forehead thermometers are more convenient but less reliable. Axillary (underarm) readings run about 0.5 °C lower than core body temperature — you need to add that amount to get a true reading.

• Rectal: Gold standard, most accurate — especially important for infants
• Ear: Practical, but recommended only from 6 months onwards
• Forehead: Quick and easy, but less accurate than rectal
• Under the arm: Least accurate; add 0.5 °C to get the core temperature

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 fever don't need medication — what they need most is plenty of fluids, light clothing, and rest. Cool calf wraps can help temporarily above 39 °C, but only when the legs are warm — they're counterproductive if the feet are cold. Medication helps when the child is visibly suffering, but only brings the fever 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
• Cool calf wraps: Only when legs are warm and temperature is above 39 °C — use lukewarm (not cold!) cloths, leave on for 10 minutes
• Rest: The body needs energy to fight — quiet activities are fine

Medication

• Paracetamol (e.g., as syrup or suppository): From 3 months and at least 5 kg body weight
• Ibuprofen: From 6 months and at least 6 kg body weight
• Never give aspirin to children under 16 (risk of Reye's syndrome)

Always calculate dosage by weight, not by age. When in doubt, read the package insert or ask your GP.

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).

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.

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). Rectal measurement is most accurate; axillary readings typically run 0.5 °C lower — add that amount to get the true value. 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).

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 longer than 3 days or rises again after a quieter phase, your GP should examine the child — this can indicate a secondary bacterial infection.

Are Cool Calf Wraps Helpful?

Cool calf wraps can provide temporary relief, but only when the legs are warm. If the feet are cold or the child has chills, cool wraps stress the circulation and are counterproductive. Use lukewarm (not ice-cold) cloths for a maximum of 10 minutes, then cover the child warmly again.

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