Alton Street Surgery Patient Information Leaflet

Blood Tests

What is a blood test?
A blood test is an analysis of a small sample of blood. Blood is the main transport system of the body, carrying hormones, antibodies, viruses, etc, as well as blood cells, and so there is lots of information that can be found out by testing it. This might include how the heart is operating, the health of the blood cells, whether there is enough/excessive amounts of protein circulating in the blood, whether waste products are being cleared from the blood by the liver and kidneys, whether a woman is pregnant, and how the immune system is functioning.

What information can be tested for?
There are hundreds of types of blood tests, depending on what information is needed. These may include:

· Haematological tests - checking the makeup of the blood itself, including the number, shape, and size of the bloodcells. May be done to check for anaemia, for example, when there aren't enough and/or the right shape of blood cell for oxygen to be carried round the body properly.

· Biochemical tests - testing for various substances carried in the blood, including hormones, glucose, iron, sodium (salt), uric acid, gases, enzymes, proteins, and drugs. The presence or lack of particular substances can indicate how healthy other parts of the body are, such as the glands (ovaries, testes, thymus, etc) or organs (heart, lungs, kidneys, liver, etc).

· Microbiological tests - checking for the presence of microorganisms in the blood, such as bacteria, viruses, fungi, and parasites, as well as the antibodies that the body may have created in response to a microorganism. When a person is tested for the HIV virus, for example, the usual test is for the antibodies to the HIV virus, as the antibodies are easier to detect than the virus itself.

How are blood samples taken?
The small sample of blood needed for testing is usually taken from a vein at the inside of the elbow, which usually only causes mild discomfort at most. A plaster is applied to the puncture site afterwards and this can be removed after ½ an hour. If more than one test needs to be done on your blood, then more than one sample may have to be taken, although in some modern laboratories many different tests can be performed on one sample. In some cases, only a very tiny amount of blood is needed, and this may then be taken via a small pinprick to the fingertip. In other, very rare, cases, arterial blood (blood from an artery, rather than a vein) may be required, and this may need to be taken from wrist or groin rather than the crook of the elbow. Having arterial blood taken may be quite uncomfortable.

Is it dangerous having blood taken?
No. As there is 4-5 litres (8 pints) of blood in an adult's body, the loss of the small amount of blood taken for blood testing has no harmful effect.

How are blood tests done?
Once the sample of blood has been taken, it is labelled clearly with your name and the reference, and what test is to be done. In some cases the blood may be allowed to clot so that the clear plasma can be tested, in others an anticoagulant (anti-clotting agent) is added to the sample so that the blood is unable to clot. The sample is then usually sent to the laboratory, where the specific test will be carried out and the results returned within a week or so. However, in the case of some tests, such as a glucose test to test for diabetes, the blood test can be done by the doctor, nurse, midwife, or even yourself in some instances.

This patient information leaflet has been adapted from an original published by Clinnix Pro, Synigence PLC