Requirements for blood donors vary somewhat from one state to another, but there are general guidelines established by the Red Cross. In most instances donors should be 17 or older, weigh at least 110 pounds, and be in good health. Some regions require 17-year-olds to get the written consent of their parent or legal guardian. You can usually give blood past age 65, as long as you comply with the weight and health guidelines, and have the approval of the blood bank doctor. Typically, all donors are advised to donate no more than once every eight weeks, but some states may have different rules. At the blood bank, be prepared to show a driver's license or other identification, and go through a screening process. The personnel will ask various questions about your medical condition to determine if you're eligible to give blood. Certain diseases like hepatitis will automatically disqualify you, as will any possible exposure to H-I-V. There are also stages in the donating process where you can anonymously drop out, with no reason needed. If your blood is drawn, it will then have to pass a series of tests for infectious diseases. For more information about blood donating requirements, speak to a doctor, or contact your local Red Cross.