Blood tests are done for different reasons. They can check your general health or look for particular substances in the blood.

how is it done?

The blood is usually taken from a vein, generally in the arm at the elbow.  A vein is one of the blood vessels that carry the blood to the heart.

To take the blood easily, you need to have a tight band put around your arm called a tourniquet, then a small needle is inserted into the vein. They can put some cream on the area, which acts like a local anaesthetic, at least 20 minutes before the blood test. This is to stop it hurting.  If you don’t have any cream, it feels a bit like a sting when it goes in. Attached to the needle is either a small blood bottle about the size of an adult's finger which draws the blood off under a low pressure or a syringe is attached which has a plunger and is pulled back to get the blood. Once they have the sample, the needle is removed and the tourniquet is taken off.

Many people don’t like to see needles or worry about seeing blood being taken and can feel faint. You will be sitting down when you have it done, but if you do feel faint let the person know who is taking the blood.

afterwards

A piece of cotton wool is put over where the blood was taken and you will be asked to press on it for a short time (1 minute) and then a plaster will be put on.

why are they done?

Blood tests are done for lots of different reasons:

• full blood count(FBC) -  this is to measure the number of red cells, white cells and platelets. More about blood counts.
• liver function tests
• kidney tests
• tumour markers – when you have some types of cancer, certain chemicals are released into the bloodstream.  These can be measured which can help to diagnose a cancer and to keep a check on how you are responding to treatment.