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📘 About the Fever Checker
A fever is a temperature of 38 °C (100.4 °F) or more measured in the ear, on the forehead or rectally — slightly lower thresholds apply to mouth and armpit readings. Enter the reading, how you took it and your child's age to see whether it's a fever and what to do.
Age matters most: any fever in a baby under 3 months needs a doctor straight away, and 39 °C or more at 3–6 months should be checked the same day. In older children how they look and behave matters more than the number.
✏️ Worked examples
2-month-old, 38.3 °C by ear
You get| Result | Fever (mild to moderate) |
| What to do | Any fever under 3 months: contact a doctor or go to hospital now |
| Temperature | 38.3 °C = 100.9 °F |
| Fever starts at | 38 °C (100.4 °F) for an ear reading |
| Get urgent help at any temperature if your child | is hard to wake, has a rash that does not fade under a glass, breathes fast or with grunting, has a fit, is not drinking or has no wet nappy for 8 hours, or you are worried |
Fever (mild to moderate) — Any fever under 3 months: contact a doctor or go to hospital now.
Try this example →3-year-old, 101.5 °F under the arm
You get| Result | Fever (mild to moderate) |
| What to do | Usually safe to care for at home: fluids, light clothing, paracetamol or ibuprofen if the child is uncomfortable |
| Temperature | 38.6 °C = 101.5 °F |
| Fever starts at | 37.2 °C (99 °F) for an armpit reading |
| Get urgent help at any temperature if your child | is hard to wake, has a rash that does not fade under a glass, breathes fast or with grunting, has a fit, is not drinking or has no wet nappy for 8 hours, or you are worried |
Fever (mild to moderate).
Try this example →❓ Frequently asked questions
What temperature is a fever in a baby?
38 °C (100.4 °F) or higher by ear, forehead or rectal thermometer; about 37.2–37.5 °C or more under the arm.
Is 37.5 °C a fever?
Usually not by ear or forehead; it can count as a low fever for an armpit reading.
When is a fever dangerous?
In babies under 3 months, at 40 °C or above at any age, or with warning signs like a non-fading rash, breathing difficulty, floppiness or a fit.
Should I treat every fever?
No — fever helps fight infection. Give paracetamol or ibuprofen if your child is uncomfortable, not just to lower the number.
What people are saying
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Anonymous · 11 Oct 2026