What is blood pressure?

Blood pressure is the force, or pressure, that makes the blood flow round the body. Blood pressure is often shortened to BP. 

  • When the heart beats, or contracts, it pushes blood through blood vessels called arteries.
  • When the heart relaxes between beats, blood returns to the heart through blood vessels called veins.  

It is very important that your child’s blood pressure is in a healthy range. If his or her blood pressure is too high or too low, your doctor will try to find out what is causing this.

High and low blood pressure

High blood pressure

Hypertension is blood pressure that is too high. In some children, hypertension can be a serious condition. It can increase the risk of getting cardiovascular disease, especially if it continues into adulthood. Some children with hypertension have no symptoms, but it may cause headaches that do not go away, vomiting (being sick) or blurred (fuzzy) vision. 

Hypertension in children is rare. If your child has high blood pressure, your doctor will try to find out what is causing it and whether it is affecting other parts of his or her body, such as the kidneys. Your child may need to make changes to his or her diet and/or take medicines.

Low blood pressure

Hypotension is blood pressure that is too low. This can happen in acute disease (where the illness comes on suddenly) or as a side-effect of some medicines. Some children with hypotension may have no symptoms, but some may experience:

  • dizziness or light-headedness
  • fainting
  • blurred vision
  • rapid or irregular heartbeats
  • nausea (feeling sick)
  • general weakness.

Your doctor will try to find out what is causing it. 

Why does my child need his or her blood pressure measured?

Children may have their blood pressure measured for many reasons, including:

  • during a doctor’s appointment – this is routine
  • when they are admitted to hospital
  • before an operation.

Regular measurements

Some children need regular measurements of their blood pressure, especially if:

  • they already have hypertension, or high blood pressure 
  • they are at risk of high blood pressure – for example, because they have problems with their kidneys.

Blood pressure measurements

Blood pressure is measured using a special instrument. This can be either electronic or manual (worked by hand).

A blood pressure measurement has two numbers. 

  • The top number is called the systolic pressure – the pressure when the heart beats. This is easier to measure and is used more often in children. 
  • The bottom number is called the diastolic pressure – the pressure when the heart relaxes.

Blood pressure changes from day to day and at different times of the day. It can also change when we feel stress and during exercise.

How is blood pressure measured?

Although measuring blood pressure will not hurt your child, it can be challenging, especially in younger children. Your child’s doctor or nurse will take a few measurements when your child is relaxed.

You do not usually need to make special preparations before your child’s blood pressure measurements. A cuff will be placed around his or her arm and pumped up, so your child will feel the arm being squeezed.

You may need to measure your child’s blood pressure at home, sometimes over a day. Your doctor or nurse will give you equipment to do this.

Blood pressure and your child’s health

Blood pressure in children

Babies, children and young people usually have lower blood pressure than adults. They have different ranges that are considered healthy. These depend on:

  • how old they are
  • whether they are a boy or a girl
  • how tall they are.

Your child’s doctor or nurse will know the normal ranges of blood pressure for children who are the same age, sex and height as your child. They will let you know what your child’s blood pressure readings mean.

Keeping healthy

Your family can follow some tips to help keep your child’s blood pressure healthy. These include:

  • eating less salt
  • eating a healthy diet
  • staying active.

If your child has a kidney condition, your doctor or nurse will give you more information about how this affects blood pressure. Rarely, children need to take medicines to control their blood pressure.

Blood pressure and kidneys

Kidneys normally control blood pressure to help make sure it is at a healthy level. They do this by regulating how much salt and water is in the blood. If the kidneys are not working properly, they may not be able to control blood pressure well.

More information

  • Hypertension

    Hypertension (blood pressure that is too high) is rare in children, and may be a serious condition. Your child's doctor will try to find out what is causing it.

  • Meet a Paediatric Nurse

    Denise and Rachel are both paediatric nurses at the Great North Children’s Hospital in Newcastle and their roles centre around the practical and emotional elements of kidney disease treatments.

  • Blood pressure and your child’s health

    Understand more about children's blood pressure, how the kidneys control blood pressure to help make sure it is at a healthy level and how you can keep the whole family's blood pressure in a healthy range.