Under 3 months, 38 °C means a doctor
The same number means different things depending on age. It's the distinction most often ignored, and the one that matters most in the early months.
The thresholds, by age
Under 3 months
38 °C or above means medical attention the same day, even if the baby looks perfectly well. A newborn can have something serious without looking unwell: their immune system doesn't yet raise the signals we'd expect in an older child. That's why the threshold is lower, and why it doesn't allow for «let's wait until tomorrow».
3 to 6 months
38 °C is already a fever. From 39 °C, seek advice without waiting for the next day.
6 months and older
| Temperature | How it reads |
|---|---|
| 37.5 °C | Low-grade |
| 38.5 °C | Moderate fever |
| 40 °C | Urgent care |
If your baby was born prematurely, the age that counts is the corrected one, not the calendar one.
What weighs more than the number
No figure replaces how they look. Seek care now, at any temperature, if any of these appear:
- Listless, or not responding as usual.
- Odd breathing: fast, laboured, or grunting.
- Not taking fluids, or far fewer wet nappies.
- Skin marks that don't fade when pressed.
- Seizures.
In NomiNest this isn't a table, it's your baby
The app works from the data you already log, and compares your baby against themselves rather than against an average.
Meet NomiNestSources. General guidance based on the American Academy of Pediatrics (AAP) and the Spanish Association of Paediatrics. With fever in a baby, the decision is the paediatrician's.
NomiNest is not a medical device and this guide does not replace your paediatrician's guidance. The information is general and orientative: every baby is different, and the professional who sees yours is the one who knows them.