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 to:
- assess your general state of health
- confirm the presence of a bacterial or viral infection
- see how well certain organs, such as the liver and kidneys, are functioning
A blood test usually involves a blood sample being taken from a blood vessel in your arm. The usual place for a sample is the inside of the elbow or wrist, where the veins are relatively close to the surface.
Blood samples from children will not normally be taken at the surgery and you will be referred to the hospital.
You can find out more about blood tests, their purpose and the way they are performed on the NHS Choices website.