Medically reviewed by Dr. Nidha P, MBBS, DNB (Paediatrics), Consultant Paediatrician
If your baby is under three months old and has a temperature of 38°C (100.4°F) or higher, stop reading and take them to a doctor now. That one is not a judgement call.
For everyone else, here's how to think about it.
What counts as a fever in a baby?
A fever is a temperature of 38°C (100.4°F) or above, measured accurately. Below that is a raised temperature, not a fever. A baby's normal temperature also varies through the day, and being wrapped up or having just fed can raise a reading slightly.
Fever itself is not the illness. It's the immune system responding to one, and the number tells you less than how your baby looks and behaves.
When does a baby's fever need urgent medical attention?
By age:
Under 3 months — any fever of 38°C or above. Go to a doctor or hospital immediately, at any hour. A young baby's immune system is immature and serious infections can progress fast with few other signs. This is the single firmest rule in paediatrics.
3 to 6 months — a temperature of 39°C or above, or any fever with your baby seeming unwell. Same-day medical review.
Over 6 months — the number matters less than how they look. A cheerful, feeding, responsive baby with 39°C is less concerning than a listless, poorly-feeding baby with 38.5°C. See a doctor if the fever lasts more than three days, or sooner with any red flag.
What are the red-flag signs?
Go to hospital immediately, at any age, if your baby has any of these — with or without a high fever:
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A rash that doesn't fade when you press a glass against it — this needs emergency care now
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Difficulty breathing — fast breathing, grunting, nostrils flaring, or the skin sucking in between or below the ribs
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Unusually sleepy, floppy, or difficult to wake
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A weak, high-pitched or continuous unusual cry
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A seizure or fit
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Blue, grey, very pale or mottled skin or lips
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A bulging soft spot on the head, or a sunken one
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Signs of dehydration — no wet nappy for 8–12 hours, no tears when crying, dry mouth, sunken eyes
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Refusing feeds repeatedly
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A stiff neck, or discomfort when light is bright
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Vomiting everything, or green vomit
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Cold hands and feet with a hot body, and mottled skin
And one that isn't a symptom: your own instinct. If you feel something is seriously wrong with your baby, act on it. Parental concern is a recognised warning sign in clinical guidelines, and doctors take it seriously.
How do I take a baby's temperature accurately?
Use a digital thermometer. For babies under three months, a rectal reading is the most accurate and is what a doctor will want, though many parents are understandably uncomfortable doing it — an underarm reading is acceptable if you tell the doctor how it was taken.
Some things to know:
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Forehead and ear thermometers are convenient but less accurate in small babies
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Never use a mercury thermometer
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Don't judge by touch alone — a baby who feels hot after being wrapped may not have a fever, and a baby with a serious infection can feel normal
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Remove extra layers and re-check after a few minutes if the reading is borderline
What helps at home?
For a baby over three months with a mild fever who is otherwise alright:
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Keep offering fluids — breast milk, formula, or water for older babies. Feed more often in smaller amounts.
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Dress them lightly. One thin layer. Don't wrap or bundle a feverish baby.
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Keep the room comfortable, not cold.
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Paracetamol may be given for discomfort, at the dose your doctor has told you, based on weight rather than age. Never exceed the stated dose or frequency.
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Rest. Let them sleep.
What not to do:
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Don't sponge with cold or tepid water. It's no longer recommended and it makes babies shiver and distressed.
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Don't use ibuprofen under 6 months without a doctor's advice.
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Never give aspirin to a child.
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Don't give paracetamol before an emergency visit in a baby under 3 months — it masks the sign the doctor needs to see.
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Don't alternate medicines on your own initiative.
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Don't judge severity by whether medicine brought the fever down. A fever responding to paracetamol does not rule out a serious infection.
What about fever after vaccinations?
A mild fever within a day or two of vaccination is common and expected, and usually settles within 24 to 48 hours. It's a sign the immune system is responding.
But the under-three-months rule still applies. A fever of 38°C or above in a baby that young should be assessed, even after a vaccination — a doctor decides whether it's vaccine-related, not the calendar.
Quick answers
How long is a fever normal? Most viral fevers settle in three to five days. Fever lasting more than three days, or returning after settling, should be reviewed.
Can teething cause a fever? Teething may cause a slightly raised temperature. It does not cause a true fever of 38°C or above. Don't attribute a real fever to teething — get it checked.
My baby's hands and feet are cold but they feel hot. Why? Cold extremities with a hot body can occur as a fever rises. Combined with mottled skin, drowsiness or breathing difficulty, it needs urgent assessment.
Is a high fever dangerous in itself? The height of a fever doesn't reliably indicate how serious the illness is. The cause matters more than the number.
What about febrile seizures? They can happen in children roughly between six months and five years and are frightening to witness. Lay the child on their side, don't put anything in their mouth, time it, and get medical help. A first seizure always needs assessment.
Should I go to the ER or wait for morning? Under three months with a fever: now. Any red flag at any age: now. Otherwise, if your baby is comfortable, feeding and responsive, morning is usually reasonable — and if you're unsure, call.
