# What temperature is a fever in a baby? | Clever Mum > 38°C or above is a fever. In a baby under 3 months, 38°C+ needs same-day medical advice (call 111 or your GP); under 6 months, 39°C+ does. For older babies * [ Home ](/) * › [ Mum Answers ](/answers) * › What temperature is a fever in a baby? Health & Safety # What temperature is a fever in a baby? Quick answer — What temperature is a fever in a baby? 38°C or above is a fever. In a baby under 3 months, 38°C+ needs same-day medical advice (call 111 or your GP); under 6 months, 39°C+ does. For older babies, behaviour matters as much as the number — a floppy, unresponsive or persistently distressed child needs help regardless of the thermometer. Trust your instincts and seek advice. ## The age-based thresholds * **Under 3 months with 38°C+**: contact a doctor or 111 the same day, even if baby seems otherwise well — young babies can't localise infection the way older children can, so fever alone earns a check. * **3–6 months with 39°C+**: same-day advice, same reasoning. * **Older babies**: the number matters less than the child. Fever is the immune system working; how they look and behave between spikes is the better signal. ## Measuring properly A digital thermometer in the armpit is the NHS-recommended method under 5 (forehead strips are unreliable; ear thermometers are fine used correctly on older babies). Don't measure straight after a bath or feed. ## Red flags at any temperature Call 999 or go to A&E if a feverish child is floppy or unresponsive, has a rash that doesn't fade under a pressed glass, struggles to breathe, has a fit, or can't be woken. Call 111 or your GP if a fever lasts more than 5 days, they're refusing all fluids with fewer wet nappies, or they're persistently distressed and you're worried. On instinct: parents who "just feel something's wrong" are right often enough that every NHS pathway tells you to act on it. Sibling guides: [fever A&E thresholds](/baby/when-to-take-baby-fever-to-ae), [glass test / non-blanching rash](/baby/meningitis-rash-glass-test-uk), [febrile seizure first aid](/baby/febrile-seizure-first-aid-uk), [croup breathing](/baby/croup-when-to-go-to-ae). **Go deeper:** [When to take a baby with a fever to A&E](/baby/when-to-take-baby-fever-to-ae/) ## More Health & Safety questions * [Are cheap baby products from Amazon or eBay marketplace sellers safe?](/answers/are-cheap-amazon-baby-products-safe/) * [Is it safe to use a self-feeding bottle prop or hands-free feeding pillow?](/answers/are-self-feeding-bottle-props-safe/) * [Are baby sleep pillows safe for a newborn or under-12-months?](/answers/are-baby-sleep-pillows-safe/) * [How do I know my car seat is fitted correctly?](/answers/how-check-car-seat-fitted/) * [Do babies need vitamin drops?](/answers/when-baby-vitamins/) [Browse every question we answer →](/answers/) Health answers describe NHS guidance and are not medical advice — for anything urgent, call 111 (or 999 in an emergency). Spotted something out of date? Email [editors@clevermum.co.uk](mailto:editors@clevermum.co.uk).