Quick answer: Paracetamol or ibuprofen at the correct weight-based dose, adequate hydration, and appropriate dressing. Do not undress or sponge with cold water — these are ineffective and cause discomfort. Any fever in a baby under 3 months is a medical emergency regardless of management.
Under 3 months: emergency, not home management
A temperature of 100.4°F (38°C) or above in a baby under 12 weeks requires emergency assessment — go to the ER or call 911, not your doctor. This is not about the height of the fever or how well the baby seems. The immature immune system of a young baby cannot localise infection, and serious bacterial infections (meningitis, septicaemia, UTI, pneumonia) can be present with only mild symptoms. In this age group, fever is a red flag that the infection source must be identified in a clinical setting. Give paracetamol to reduce discomfort while travelling to hospital — not as a wait-and-see home treatment.
Over 3 months: paracetamol and ibuprofen
Paracetamol (from 2 months, 4kg+): 15mg per kg of body weight, every 4–6 hours, maximum 4 doses in 24 hours. Children’s paracetamol suspension: 120mg/5ml is standard in the UK. A 6kg baby needs 90mg = 3.75ml. Ibuprofen (from 3 months, 5kg+): 5–10mg per kg, every 6–8 hours, maximum 3 doses in 24 hours. Has anti-inflammatory effect in addition to fever-reducing — useful when fever is from an inflammatory process. The two can be given together or alternated for better sustained management, on medical advice for the alternating approach. The goal of fever management is comfort, not achieving a normal temperature — a low-grade fever suppressed to normal by medication is not the target.
Hydration during fever
Fever increases fluid requirements significantly — each degree above normal increases fluid loss by approximately 10–12%. Increased breastfeeding frequency; more frequent formula feeds in smaller amounts; sips of cooled boiled water for babies over 6 months. Signs of adequate hydration: pale yellow urine, normal alertness. Signs of dehydration warranting doctor contact: very concentrated (dark) urine, sunken fontanelle, dry mouth, unusual lethargy, very few wet diapers.
What not to do
Cold sponging or tepid baths: these cause shivering (increases metabolic rate and body temperature) and discomfort. No longer recommended by NICE. Undressing: removing all clothing causes heat loss by convection and shivering — dress appropriately (one layer less than usual, not naked). Aspirin: not under 16 years (Reye’s syndrome risk). Alternating paracetamol and ibuprofen routinely without medical guidance — this can lead to dosing errors. Measuring fever by hand: unreliable; use a thermometer.
Frequently Asked Questions
Should I always give medicine for a fever?
Not necessarily — a fever is the immune system working. Treat the child, not the number: if the baby is comfortable (feeding well, responsive, not in distress), observation without medication is appropriate. Give medication if the baby is clearly uncomfortable, in pain, or refusing to feed due to feeling unwell. A baby with a fever of 103.1°F who is feeding, alert, and interactive needs less urgent intervention than a baby with a fever of 38.2°C who is very lethargic and refusing feeds.
The fever came down with paracetamol but came back — should I be worried?
Fever recurrence after paracetamol wears off (typically 4–6 hours) is normal with viral illnesses. A fever that persists for more than 5 days, or that is accompanied by worsening rather than improving overall condition, warrants doctor assessment regardless of how it responds to paracetamol.
When should I go to the ER for fever in a child over 3 months?
Go immediately if: non-blanching rash (press a glass against it — if the rash doesn’t fade, go immediately); stiff neck; severe headache; sensitivity to light; difficulty breathing; unusual drowsiness or difficulty rousing; blue lips or tongue; temperature above 104°F that doesn’t respond to medication; and always for any child under 3 months with any fever.
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