A blood test may provide clues to health problems, like heart or kidney conditions. However, initial test results that are abnormal are usually followed by additional testing that can help make a definitive diagnosis. Additionally, other tests may be performed to determine the cause of the condition so that it may be treated appropriately.

Typically, a blood sample is taken by inserting a needle into a vein, usually in your arm. Before your blood is drawn, an elastic band is tied around your upper arm to increase blood in the veins, and the puncture location is wiped clean with an antiseptic. A blood draw using a needle may cause a temporary sting. The blood draw normally lasts for less than a minute. Sometimes a blood sample is collected by puncturing the tip of a finger and drops of blood are collected onto a test pad, filter paper, or into a small tube. Find out what happens to your blood sample after it is collected by reading

Laboratory tests are among the most common and important tools of modern medicine. Results from clinical laboratory tests contribute to the majority of health care decisions. They provide information about your health status and risk factors and can be used to determine a diagnosis, guide therapy, and estimate outlook (prognosis). Many of the decisions you and your health care provider make about your care are based on results of laboratory tests.