While it can be concerning if you or someone else has a high temperature, it's a healthy response by the human body. Most of the time, you won't need to measure your body temperature as it's likely that your body can naturally regulate it on its own.

There may be times, however, that you are concerned that you or someone else has a high temperature. It's essential to seek medical help if you have a young baby with a high temperature or if there are other symptoms that you are worried about.

You can normally tell if someone else has a temperature by placing your hand on their forehead, back or chest. If you have a high temperature, you may alternate between feeling too hot and too cold or have uncontrollable shivers. To get a more accurate idea of your own or someone else's body temperature, you can also use a thermometer.

In this guide, we'll look at how you can measure your body temperature, what a normal temperature is and what you should and shouldn't do when you have a fever.

Depending on where you are in the world and which units you use, body temperature can be measured in Fahrenheit (°F) or Celsius (°C). You can use a thermometer to take your temperature, which can be helpful if you want to see if you have a fever.

Most digital thermometers will allow you to change the units so that you can easily read and understand your body temperature. It's a good idea to keep the same units if you are studying your body temperature over a period of time so that there isn't any confusion when comparing the different readings.

Most people take their temperature by inserting a digital thermometer into their mouth. Before you do so, however, make sure that the tip of the oral thermometer has been thoroughly cleaned with cold water and soap. To orally take your temperature, you need to place the thermometer underneath your tongue and near the back of your mouth. Close your mouth and wait until the thermometer signals that your oral temperature has been recorded. This could be when the thermometer beeps or flashes.

Below are the various other ways that you can take your temperature.


You can take your temperature by inserting a digital thermometer into your ear. It's helpful to gently pull your ear up and backwards so that you can gain better access. If you use a digital thermometer correctly by following the instructions, it's unlikely that you will push the thermometer too far into your ear canal.


To take your temperature via your armpit, you need to securely place the thermometer in your armpit and lower your arm. Ideally, your elbow should be held against your chest, so the thermometer is held tight. Keep the thermometer in place for the length of time recommended in the packaged instructions.

Although it can be a good indicator of your body's temperature, the armpit should be used as a last resort as it isn't as accurate as other methods.


Some digital thermometers can take readings from your forehead. This is a quick way to take your own or someone else's temperature, but the reading won't be as accurate as an oral reading. The temperature of your forehead will usually be between 0.5 to 1 degree lower than the temperature in your mouth.


Although most people avoid it, the best way to take an accurate reading of your body temperature is via your rectum. This method is often used by medical professionals as it gives the best indication of someone's temperature, as your rectal measurement is a good indicator of your core body temperature.

You should place a lubricated rectal thermometer into the rectum up to around 1/2 to 1 inch (1.3 to 2.5 centimeters) for an accurate reading. It can be harmful to force the thermometer in past the point of resistance, so be careful when taking rectal temperatures.

How do I take a child's temperature?

Babies and children under the age of five should have their temperature taken by placing the thermometer under their armpits. To do this, you should place the child on your lap and place the thermometer in their armpit. You will need to gently but firmly hold the thermometer in place while the thermometer takes the reading. This will usually take about 15 seconds.

You can take an older child's temperature using the same methods you would use for yourself. Most parents prefer to take their child's temperature by inserting the thermometer into their mouth. If you choose to do it this way, it's a good idea to wait until at least 15 minutes after your child has eaten or had a drink so that the readings aren't affected. You can also take their temperature by inserting the thermometer into their ear.

Your body temperature may be raised if you are wearing multiple layers of clothing or if you have been in a warm or sunny room for a period of time. In the same way, a cold room can affect the accuracy of a thermometer reading. The thermometer may also show a raised temperature if you have recently had a hot bath, been active or held a hot water bottle. A sweaty forehead may also affect the accuracy of the thermometer reading.

It's a good idea to allow yourself or your child to cool down for a few minutes before you take the temperature measurement. This could mean leaving a warm room or removing excessive layers of clothing. Try not to let yourself or the other person become cold or shivery, as you will need to take their body temperature again to see if their temperature changes again.

It's not essential that you take your temperature unless you are advised to by your doctor or another medical professional. You may have a fever even if the thermometer doesn't show a high reading, or you could feel fine even if the thermometer shows a high body temperature.

Some people choose to take it every few hours when they feel unwell. This can help you monitor whether your temperature is rising or falling and if you need to seek medical help.

It's considered a high temperature if your thermometer shows readings of around 100°F (38°C) or higher. Humans have a normal temperature range of between 97°F to 99°F (36°C to 37°C). Babies and children typically have a temperature of 97°F (36.4°C), although this can vary depending on the child. You should seek medical help if you have a baby under three months old with a temperature over 100°F (38°C) or if you have a child aged between three and six months who has a temperature over 102°F (39°C).

You should check if your temperature is high, if your chest or back feels hotter than usual, or if you feel shivery. If you find that you have a fever after taking your temperature, you should make sure to drink plenty of fluids and rest.

What causes a high temperature?

A high body temperature is called a fever and is your body's natural response when you are unwell. You will have an increased amount of white blood cells to help you fight the infection, which will affect your body's temperature. When you have a fever, your body will try to cool itself down through sweating. If you aren't sweating when you have a high temperature, this could mean that you are dehydrated or that your body isn't fighting the infection properly.

While a high temperature should come down on its own after a few days, it's advisable to seek medical help if it persists or is accompanied by other symptoms, such as a rash.

Some people may get a high temperature after having a vaccination. This should go away by itself within 24 to 48 hours, although you may want to take painkillers to help lower the fever.

A fever should go on its own within a few days, although you could take acetaminophen or ibuprofen to help you feel better in the meantime. You should drink plenty of fluids to make sure that you stay hydrated, as well as get plenty of rest so that your body can fight the infection. It's a good idea to avoid alcohol and caffeinated drinks while you have a fever, as they can increase your chances of becoming dehydrated.

Avoid putting on too many clothes or blankets while you have a fever. This can make your fever worse as it will disturb your body's thermoregulation. Equally, you shouldn't take a cold bath or a cold shower as this can lead to further shivering, which will increase your body temperature again. You could try a warm bath or shower instead, as your body will cool as the water evaporates.

Although many people have heard the old saying 'feed a cold, starve a fever', you should continue eating food to help boost your immune system. You will burn more calories if you have a high body temperature, so you should eat as much as you feel able to. It's also advisable to get as much sleep as possible, as your body will need time to recover and boost your immune system.

Your body will need a lot of your energy to fight your illness. For this reason, you should try to reduce or stop your usual activities so that your energy isn't used up by less important tasks. It's a good idea to stay at home and away from other people until 24 hours after your fever has gone.

What is basal body temperature?

Basal body temperature (BBT) is your lowest resting body temperature and is usually reached during sleep. Some women take their BBT each morning and chart it as a way to try and understand their fertility cycles. However, some reports indicate that BBT is only 70% accurate at predicting fertile days.

When you ovulate, your body temperature may increase by around 32°F to 33°F (0.2°C to 0.6°C) over the course of a few days. By measuring your daily temperature, you will be able to tell when you have ovulated, which could help you to predict when your next ovulation will be.

Is a digital thermometer better than a mercury thermometer?

There isn't a major difference between the accuracy of digital and mercury glass thermometers. However, digital thermometers are far safer to use than mercury thermometers and are, therefore, more popular.

Before digital thermometers became the default method for measuring body temperature, glass thermometers were the most common method. A mercury glass thermometer is able to measure liquid, vapor and body temperatures. The mercury inside glass can expand and contract when it reacts to changes in temperature. Once the liquid mercury has settled, you can look at where it has reached on the thermometer's scale, which will indicate the recorded temperature.

Although the mercury thermometer measurement method can give accurate readings, it has largely been replaced by digital thermometers due to safety concerns. The glass tubes can break, and the mercury inside is a toxic metal that can prove fatal if it is consumed or inhaled.

You can measure body temperature by using a digital thermometer. Taking an oral or rectal temperature measurement is the most accurate way to find out your core body temperature. You can also use a thermometer on your forehead or under your armpit to find out your skin temperature. This will usually be a few degrees cooler than your core body temperature, however.

It's important to remember that your body temperature varies due to various internal and external factors. The temperature of the room or the amount of clothes that you are wearing can change your body temperature. You are likely to have a high temperature if you are unwell, as it's one of your body's ways of fighting infection. It can help to take medication such as acetaminophen or ibuprofen if you feel unwell.