Blood culture is microbiological culture of blood. It is employed to detect infections that are spreading through the bloodstream. In medicine venipuncture or venepuncture is the process of obtaining a sample of venous blood. Usually a 5 ml to 25 ml sample of blood is adequate depending on what blood tests have been requested. In many circumstances it will be done by a phlebotomist, although nurses, doctors, some EMTs, paramedics, other medical staff and chiropractors are also trained to take blood. Blood is most commonly obtained from the median cubital vein, on the anterior forearm (the side within the fold of the elbow). This vein lies close to the surface of the skin, and there is not a large nerve supply.Minute quantities of blood may be taken by fingersticks sampling and collected from infants by means of a heel stick or from scalp veins with a butterfly needle