Fever in babies less than 3 months of age is much more likely to be due to a serious infection that needs urgent treatment than a fever in an older child. All children under 3 months of age with a temperature above 38°C (100.4°F) should be seen by a healthcare professional. The only time your baby doesn't need to see a doctor with their fever is if they have had their vaccines in the last 48 hours (given from 8 weeks of age) .
If your baby has had their vaccinations in the last 48 hours follow the advice given by your community nurse at their vaccination appointment.
You should measure your baby’s temperature under their armpit. Hold their arm against their body to keep the thermometer in place for however long it says in the manufacturer's instructions – usually about 15 seconds; some digital thermometers beep when they're ready. You should not measure their temperature on the forehead or in their ear – it will not be accurate in young children.
How to take a temperature