If it's the middle of the night and your baby feels warm, take a breath. Fever is one of the most common reasons parents worry, and most of the time it's a sign that your baby's body is doing exactly what it should — fighting off a bug. This guide will help you read the whole picture, not just the thermometer.
What actually counts as a fever?
A fever is generally a body temperature of 38°C (100.4°F) or higher. That number is the same across Australian, US and WHO guidance.
But here's the most important thing: a fever is not about the number alone. A baby with a temperature of 38.5°C who is feeding, settling and giving you the occasional smile is usually less worrying than a baby at 38.1°C who is floppy, pale and very hard to rouse. How your baby looks and behaves tells you more than any single reading.
Under 3 months: always take it seriously
This is the one rule we never soften.
Older babies and toddlers have more robust immune systems, so a fever in a 9-month-old is judged much more on how they're coping than on age alone.
Keeping your baby comfortable
The goal of treating a fever isn't to force the number down — it's to help your baby feel better.
- Offer extra fluids. Keep up breastfeeds or bottle feeds, more often if needed. Fever increases fluid needs.
- Dress lightly. One light layer is plenty. Don't bundle or "sweat it out," and skip cold baths or sponging — these can make babies shiver and more uncomfortable.
- Keep the room a comfortable temperature. Not hot, not cold.
- Rest and cuddles. Plenty of skin-to-skin and quiet time helps.
- Medicines: paracetamol or ibuprofen may help an older baby who is miserable — but ibuprofen isn't for babies under 3 months (and check local guidance, as US advice says 6 months), and dose by weight following the packet or your pharmacist. Always check with your pharmacist, GP or child-health nurse first — and never use medicine to bring down a fever in a baby under 3 months without medical advice.
Red flags — when to get help now
Trust your instincts. You know your baby. Seek care urgently if you notice any of these:
| Watch for | Why it matters |
|---|---|
| Any fever under 3 months of age | Urgent — see a doctor straight away |
| Trouble breathing, fast or grunting breaths | Possible serious illness |
| A rash that doesn't fade when pressed | Can signal a serious infection |
| Very drowsy, floppy, or hard to wake | A change in alertness is a key warning sign |
| Fewer wet nappies, no tears, dry mouth | Signs of dehydration |
| A seizure, or a stiff neck / bulging soft spot | Needs emergency assessment |
| Fever lasting more than 2 days, or you're simply worried | Always okay to check in |
A few reassuring facts
- The height of a fever doesn't reliably predict how serious the illness is.
- Most fevers in babies are caused by everyday viral infections and pass on their own.
- A mild fever after vaccinations is common and usually settles within a day or two — your nurse can tell you what to expect.
The bottom line
Look at your whole baby, not just the thermometer. Keep them comfortable and hydrated, and watch how they're behaving. For any baby under 3 months with a fever, or any red flag at any age, seek care without delay. When in doubt, your GP or child-health nurse is always the right person to ask.