MODEL RELEASED. Blood donation. Blood donor lying down, with a tube inserted in her forearm to collect blood. She is squeezing a cylindrical object to encourage good circulation in her arm. The blood collects in a bag (not seen) that is suspended beneath the bed. Usually about 475 millilitres of blood is collected. In her hand the nurse is holding two sample tubes containing the donor's blood that will be screened for blood diseases, such as hepatitis and HIV, and typed to determine the blood group. Donor blood is given to patients in transfusions to replace lost blood, for example during surgery or after accidents.