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. and 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 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.
When coming for a blood test, please drink plenty of water on the morning of your appointment. This makes it easier to find your vein and take your blood.
Also, please rearrange routine blood tests if you have a virus - attending when unwell spreads the virus in the community.
When you have a blood test, you will need to book a morning appointment. This is because the hospital transport collects blood test specimens at lunch time.
Fasting Blood Tests
If you are having a "fasting" blood test, you must not eat or drink anything except water from 9.00pm the night before your blood test. For fasting blood tests you should try and book your appointment for as early in the morning as possible.
Warfarin Blood Tests
When you initially start taking Warfarin medication it is important that you book appointments for the day advised to you. However, once you are established on this medication it is not essential for you to have your repeat blood test on the specific day advised - a day earlier or a day later if needs be is acceptable.
Blood Test Forms
If you are having a blood test performed at the request of a hospital specialist, you should have been given a form detailing the tests required. Please bring this with you to your appointment.
You can find out more about blood tests, their purpose and the way they are performed on the NHS Choices website.