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 the phlebotomist taking a blood sample from a blood vessel in your arm, the usual place to take a sample from is the inside of the elbow or wrist, where the veins are relatively close to the surface. Blood samples from children are most commonly taken from the back of the hand.
You can find out more about blood tests, their purpose and the way they are performed on the NHS Choices website.
It is important to realise that laboratory results may be outside of the so-called “normal range” for many reasons, such things as race, age, degree of physical activity, problems with collection and/or handling of the specimen and a large number of non-illness-related factors. The ‘normal range ‘ also only covers 95% of patients which mean that 5% of healthy patients fall outside of the normal range, even when there is nothing wrong with them.
It is also important to realise it is not usually possible to diagnose a disease with a blood test alone. It may, however, help you to learn more about your body and detect potential problems in early stages when treatment or changes in personal habits can be most effective.