It is not unusual for babies and small children to get a mild fever. A fever is often a sign that your baby is fighting an infection however as a parent it is natural to be concerned.  For that reason, it’s important that you know the difference between what is a ‘normal’ temperature and a high temperature or may need medical attention.
What is normal body temperature for a baby?
The Sydney Children’s Hospital states that a baby’s body temperature should range between 36.5 and 37.5 degrees Celsius  A temperature of 38.0 degrees Celsius or more in a baby under three months of age, and 38.5 degrees Celsius or more in older infants is considered significantly high. 
If your baby is showing signs of a fever, you should take their temperature with a thermometer; you may find a digital thermometer is the easiest to use and the most accurate. Normal temperature varies depending on whether you take an internal or external reading, so it’s important to know what to look for depending on and what part of the body you are taking the reading from.
- Normal temperature range with an ear thermometer is 35.8 to 38.0 degrees Celsius. 
- Normal oral temperature should be between 35.5 and 37.8 degrees Celsius. 
- Normal armpit temperature should be below 34.7 to 37.3 degrees Celsius. 
- For rectal thermometers, the normal range is 36.6 to 38.0 degrees Celsius. 
As always, get in touch with a GP or healthcare professional if you’re concerned.
What are the different types of thermometer?
- There are several methods of taking an infants temperature such under the tongue, under the arm, in the ear or forehead . The method you choose may be dependent on what thermometer you use.
- Digital thermometer – These are quick to use and very accurate. These types of thermometers are generally used for taking under the arm readings.
- Ear thermometer - This type of thermometer is the quickest way to take a baby’s temperature as it can give a reading in just 1 second. However this type of thermometer is expensive and you must follow the instructions carefully to make sure you get an accurate reading.
- Strip – type – These are very basic thermometers that you simply hold against your baby’s forehead.
- Mercury – This method is very dated and no longer used. It can be dangerous due to the fact that the thermometers can break into small shards of glass and release poisonous mercury. It is best to avoid the use of mercury thermometers in infants for this reason. 
How often should you check your baby's temperature?
When your baby has a fever you should be regularly checking their temperature and level of discomfort to make sure they are okay, however it’s important that your baby gets as much rest as possible to help fight the infection or virus causing the fever. Using a traditional digital thermometer can disrupt your baby’s sleep but the Nurofen FeverSmart Temperature Monitor helps address this problem. The wearable patch is synced to an app on your smartphone meaning you can monitor your baby’s temperature continuously without needing to disturb them, giving you peace of mind and making sure your baby gets plenty of rest. It is still advisable to check on your child in person, as usual.
While it’s horrible to see your baby feeling under the weather, most will recover from a fever after a few days without further treatment. If your baby is under six and has a high temperature, you should visit your GP or speak to a healthcare professional immediately. For older infants, keep them comfortable, encourage them to drinks lots of fluids to prevent dehydration and be sure to keep the room well aired. Again, if you are worried, get in touch with a GP or healthcare professional.
 Canadian Paediatric Society, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2819919/