The test involves drawing blood from a vein in the arm or hand.
Obtaining a blood sample from a vein takes a few minutes and generally causes only minimal discomfort. Occasionally, some people may feel queasy or light-headed while the blood is drawn or shortly after. Taking slow deep breaths is usually enough to calm these feelings. Some people may develop a small mark or bruise.
Typically, doctors will send these samples to a lab for assessment and relay results to the patient in due course.