This overview is a sample of the type of information available to you at Griffin Hospital's Community Health Resource Center. It is not intended to replace your physician's instructions in the management of your health problems, but to better inform you about a particular illness and alert you to the availability of other materials. If you have a question about any piece of information presented in theses fact sheets, please call your physician, or stop by the Community Health Resource Center at your convenience.

BLOOD TESTS

Blood can be tested for a wide variety of substances including sugar, minerals (also called electrolytes), hormones, and antibodies. By analyzing your blood, your doctor can determine whether you have anemia, an infection, how effectively your blood can clot, as well as the condition of your heart, liver, and kidneys.

For most blood tests, a laboratory technician will draw the blood sample out of a vein. (This process is called a venipuncture.) He or she will probably use one of the veins on the inside of your elbow since these are large and near the surface in most people, but any vein can be used.

An elastic band, or tourniquet, is first applied around your arm which will cause the blood to back up, making your veins bulge. Alcohol or iodine is used to clean the skin over the vein. A hollow needle will then be inserted into the vein and the blood will be drawn into tubes or into a syringe. The tubes may have different colored tops. This indicates to the lab what the blood is to be tested for.

The only pain in a blood test will be when the needle pricks the skin. Leaving the needle in place while several tubes of blood are drawn will not be painful. Some people have veins that are "hard to find," meaning that it is difficult to draw blood from many of their veins. If you know which vein has been used to easily draw your blood in the past, mention this to the lab technician to avoid being stuck more than once.

When all the blood samples have been collected, the tourniquet will be released and the needle removed. A piece of gauze or cotton will be held firmly over the puncture site for a few moments to prevent bleeding and then a Band-Aid or tape will be applied. Sometimes a bruise appears at the site, but it should go away in a few days.

It may seem as though you are losing large amounts of blood but this is usually not a problem. Your body will quickly replace the lost blood volume. However, if many blood tests are performed frequently, your doctor or nurse may request that smaller tubes be used for the samples.

If the blood test requires only a small amount of blood, the sample can be obtained by a finger stick rather than by drawing blood from a vein. Blood sugar can be tested in this way and may be performed several times a day. The fingertip is first cleaned with alcohol and then pierced with a small, sharp piece of metal called a lancet. Blood is then squeezed out into a tiny glass tube. Afterwards, you will be asked to apply pressure to the puncture site to stop the bleeding.

All blood tests require that the blood be sent to the lab. The results will be available in a few hours or days, depending on the test. Your nurse or doctor can inform you of the results.

Please note that this information is intended to give you a general overview of the topic. It is not intended to replace advice or instruction of a health professional. We recommend that you consult your physician, nurse, or qualified health professional regarding the information in this publication. © 1994 Planetree, Inc. Reproduction of this material in any form is limited to license agreement.

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