A blood test is when a sample of blood is taken for testing in a laboratory. Blood tests have a wide range of uses and are one of the most common types of medical test. For example, a blood test can be used:
- for a healthy person to assess the risk of disease (e.g. cholesterol check to help find out the risk of heart disease, or blood sugar to screen for diabetes)
- to diagnose the cause of symptoms (e.g. anaemia or thyroid disease)
- to monitor a condition or its treatment (e.g. check kidney function in those on treatment for blood pressure)
- for employment or visa requirements (this is not normally covered by the NHS and will require payment)
A blood test usually involves the phlebotomist taking a blood sample from a vein in your arm, usually at the inside of the elbow. Blood samples from children are most commonly taken from the back of the hand. The child's hand will be anaesthetised (numbed) with a special cream before the sample is taken. Children under the age of five and those with very difficult veins may be referred to the hospital for phlebotomy.
You can find out more about blood tests, their purpose and the way they are performed on the NHS Choices website.