Phlebotomy
Phlebotomy, also known as a blood draw or venipuncture, is the process of withdrawing blood from a vein to send it to a laboratory for testing. Blood draws are performed for three major reasons: to identify potential health issues before symptoms arise, to confirm diagnoses when symptoms are present, and to help monitor disorders and treatments. One blood sample can be tested for numerous conditions.
Reasons for Phlebotomy
Phlebotomy is used to measure both the components of the blood (cells) and the levels of a variety of substances the bloodstream (serum or plasma) carries. A complete blood count (CBC) measures the number of cells in the blood, including red blood cells, white blood cells, and platelets. Other blood tests are performed to evaluate whether the patient has normal levels of many substances, including:
- Glucose
- Electrolytes
- Blood gases
- Pathogens
- Enzymes
- Proteins
- Creatinine
There are normal ranges for each substance found in the blood and an abnormal reading may indicate the presence of a disease or a chronic condition. It is also possible that the abnormal result is simply the result of medication or a dietary imbalance. Sometimes, a blood test with an abnormal result may be repeated to see if the results remain constant. If so, further diagnostic testing will be done.
The Phlebotomy Procedure
The veins of the arm are typically the best location for phlebotomy, so a blood draw is normally performed at either the inner elbow or the back of the hand. Once the skin in the area is cleaned, an elastic band is tied around the upper arm to increase the volume of blood in the lower arm. The patient is asked to make a fist for the same reason.
A needle connected to tubing and a collection vial is inserted into the vein. This may cause minor discomfort. After the necessary amount of blood is withdrawn, the needle is removed and the injection site is cleaned again and covered with a bandage. The patient is asked to apply pressure to the site for a few minutes to assist the blood in clotting.
The blood sample taken is then sent to a laboratory for processing. Depending on the nature of the specific blood tests, the results will be available in 24 hours, a few days, or a few weeks.