What temperature means a fever for a baby? And when to seek medical help

I know I can tell you, as a GP, that a fever is common and that it is in all likelihood related to a simple viral infection but, as a mother, I also know how horrible it is when your small child is unwell.

What temperature is a fever in babies?

For babies, 38°C (101°F) is the temperature that's officially classed as a fever.
A normal temperature for babies and children under 5 is 36.4°C (97.5°F), which is slightly lower than a normal temperature for adults (37°C) but this varies slightly between children and even in your child each day. We all exist within a small range of temperatures.

What temperature is a fever for toddlers and older children?

It's the same: 38°C (101°F) is classified as a fever for all babies, toddlers and children.

My baby has a fever: should I see a doctor?

This all depends on how old your child is, how high their temperature is, how long they've had it, and what other symptoms they have...

If your baby is under 3 months old, you should take them to a doctor if they have a temperature of 38°C (101°F) or higher. This is this is even more important if your baby is under 1 month old
If your baby is between 3 to 6 months old, you should take them to a doctor if they have a temperature of 39°C (102°F) or higher
No matter what your baby's age is, you should take them to a doctor if they have a fever that's lasted for 5 days

Your first port of call is your GP but, if it's a weekend or the practice is closed, call NHS 111 or contact your local GP out-of-hours service.

But if your child also isn't drinking or urinating, or if they are drowsy, floppy, or can't be roused, then you’ll need urgent medical attention.

What fever symptoms should I look out for, so I can check my baby's temperature?

Your baby may have a fever if:

They have flushed, rosy cheeks
They feel especially sweaty or clammy to touch

What about the touching their forehead? Yes, your baby may have a fever if they feel hotter than usual when you touch their forehead – or back or tummy – but this is not such a clear fever symptom as the ones above, as it can be affected by the number of layers of clothes your child has on or by very warm weather.

If you think your baby has a fever, check their temperature with a reliable thermometer.

Which kind of thermometer is best for taking a baby's temperature?

For babies, I'd recommend a digital thermometer that you place under your child's armpit. You can find these online or at pharmacies and bigger supermarkets.

More expensive digital thermometers that you place in your child's ear (tympanic thermometers) are also available. These are great but can give misleading readings if you don't put them in your baby's ear correctly – which is quite likely to happen with a small baby as their ear holes are so small. I'd say it's probably best only to use an in-ear thermometer for your baby from about 6 months old. You can, of course, continue to use an armpit one from 6 months, too – in fact, the NHS suggests you use an armpit thermometer for preference until your child is 5.

Forehead thermometer strips are not recommended as they can give inaccurate results: they can be affected if you are in direct sunlight or if the forehead is wet or sweaty.

How can I make sure I get an accurate temperature reading?

First, you'll need a good thermometer to make sure the readings can be trusted. It's a good idea to check the thermometer has been tested to give a reading within 0.2°C accuracy.

Then pick your moment. If your baby has just had a warm bath, been in a very warm room, been very active or been wrapped up in a blanket or been wearing lots of clothes, this may have elevated their temperature, so allow them to cool down for a few minutes before using the thermometer.

To do this, sit your baby on your knee and put the thermometer in their armpit. Gently close your child's arm over the thermometer, keeping their arm gently pressed against their body to stop it falling out. The length of time the thermometer needs to stay there will depend on the model of your thermometer (check the instructions) but, once the required time has elapsed, the digital display will show your baby's temperature.

Is a high temperature the same as a fever?

It depends! The words 'high temperature' and 'fever' are often used interchangeably – by doctors as well as parents and carers. But some people do think of them as having slightly different meanings – with fever being (rightly) reserved for temperatures of 38°C or over and high temperature used for a temperature – such as 37.5°C – that's higher than normal but just under the fever threshold.

If your baby has a high temperature under this definition, it's a case of waiting and watching– to see if their temperature rises to a fever level or (hopefully) returns to normal.

It may help to remember the following:

36.1°C to 36.4°C: considered a normal temperature for babies
36.4°C: the official normal temperature for babies
37°C: considered a normal temperature for babies
37.5°C: high temperature
38°C: fever

How can I bring my child's temperature down?

Remember: if your baby has a fever and they're under 3 months of age, they should be assessed by a doctor.

For babies over 3 months, the first thing to say here is that you don't necessarily need to treat your child if they have a fever. The rule of thumb is to "treat the child, not the fever".

This means that if your child has a fever of, let's say, 38.8°C but is as alert and active as usual, and drinking and weeing as usual, then it may not be necessary to give medication. If, however, your child has a fever of 38°C but is miserable, only wants to cuddle, is drinking less and weeing less, then it is time to treat, even though the actual temperature is lower than in the first example.

If treatment is required, then an age-appropriate dose of paracetamol OR ibuprofen can be used: do make sure you follow the instructions on the bottle. Paracetamol shouldn't be given to babies under 2 months, and ibuprofen shouldn't be given to babies under 3 months of age, unless advised by a doctor.

Once you give your baby the medication, their temperature may not return completely to normal levels but if it doesn’t come down at all with paracetamol or ibuprofen, then your baby needs to be seen by a doctor.

The medication treats the fever, not the cause of the high temperature, so it often rises again as the medication wears off. Do be careful to stick closely to the guidance on the bottle about how often you can give the medication, as well as how much. I recommend writing down the times at which you give each dose, so that you can ensure you don't give more than the recommended number of doses in 24 hours: after disturbed sleep with an unwell child, it can be difficult to remember!

What else can I do to make my baby more comfortable with a fever?

It is distressing when your baby isn't well but there are a few things you can do to help them feel better when they have a fever.

Encourage them to drink lots and offer regular feeds if you're breastfeeding
Remove layers. Strip your baby down to their vest and nappy – or even just their nappy if the weather's warm. At night, use only a single sheet to cover them as they sleep
Soothe with a damp flannel on your baby's forehead
Keep the room cool: open a window and, if it's hot weather outside, maybe turn on a fan, if you have one
Keep them at home if they usually go to nursery, a childminder or playgroup

It's also important to look out for signs of dehydration, such as fewer wet nappies, a dry mouth, no tears, and sunken eyes and seek help if you notice these.

As always, if you are concerned about your child's health then please seek medical advice.

Pics: Getty

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Dr Philippa KayeGP

Dr Philippa Kaye works as a GP in both NHS and private practice. She attended Downing College, Cambridge, then took medical studies at Guy’s, King’s and St Thomas’s medical schools in London, training in paediatrics, gynaecology, care of the elderly, acute medicine, psychiatry and general practice.