Diagnosis using blood tests
A blood test is taken so that the blood can be analysed in the laboratory. It is usually used to look for a bacterial or viral infection, or to see how certain body organs are currently functioning, such as the liver or kidneys.
It is a simple procedure where a special needle is inserted, usually into the crook of the elbow, and an amount of blood is extracted into a small bottle by a nurse. The contents are then sent off to be analysed and the results sent to your consultant.
What to expect during a blood test
You will usually require little or no preparation for the test but, in some instances, your doctor may request a period of fasting ahead of the test. This means you may need to have nothing but a small amount of water from bedtime the night before the test. However, you will be advised of this when the test is booked.
It is the most routine test that is performed and once the blood is taken, a small dressing is applied to the place where the blood is taken to help prevent any bleeding and bruising. Very occasionally people may feel faint or dizzy during or after the test so you are monitored for a short period after the blood has been taken whilst the dressing is applied. If this is the case, please tell the person performing the test.