Blood Tests
How is a blood test normally done?
Your name and other details are written on a form and blood bottles.
The vein used for blood sampling is usually on the inside of your elbow or back of your wrist.
A tourniquet (tight band) is usually placed around your upper arm. This makes the vein fill with blood and makes it easier for the blood sample to be taken.
The skin over the vein is usually cleaned with an antiseptic wipe.
A needle is then inserted into the vein through the cleaned skin. The needle is connected either to a syringe, or directly to blood sample bottles.
When the required amount of blood is taken, the needle is removed. The small wound is pressed on with cotton wool for a few minutes to stop the bleeding and prevent bruising. A sticky plaster may be put on.
Blood is placed in bottles.
Variations of blood taking
Some blood tests require several samples taken over a period of time. For example, they may be done to check how you respond to something. If you require repeated samples fairly close to each other (over the next few hours or so) a doctor may insert a 'butterfly' needle into the vein which can be taped to the skin. Samples of blood can then be taken without using a needle each time.
If only a small amount of blood is needed (for example, for checking blood sugar using a test strip of paper) then a few drops of blood can be squeezed out from a small prick in the tip of the finger or earlobe.
Some blood tests are taken from an artery in the wrist. For example, when the level of oxygen in the artery is checked. This is usually only done in hospital in certain circumstances.
You may be told to not eat for a certain length of time before certain tests. For example, a test of blood glucose is commonly done first thing in the morning before you have anything to eat.
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