It is also used to help diagnose many disorders, including problems with a person's blood, heart, kidney and nutritional status. A blood sample is taken from a vein on the forearm or hand. First, the skin over the vein is cleaned with an antiseptic. This enlarges the veins in the lower arm by restricting blood flow through them. A fine needle is gently inserted into a vein, and the tourniquet is removed.
Blood flows from the vein through the needle, and is collected in a syringe or vial.
After the needle is withdrawn, the puncture site is covered with a bandage for a short time to prevent bleeding. A person should request specific instructions from his or her healthcare provider. This can occur with conditions such as severe diarrhea. Erythropoietin is a hormone made in the kidney. Eclampsia is a serious condition involving high blood pressure, protein in the urine and swelling of the face and hands during pregnancy.