Blood is a red fluid that circulates through our bodies in veins and arteries. It acts as the body's transport system and helps fight infections. Blood cannot be manufactured and must come from donors to help patients in need. Donating blood is important to maintain a safe and reliable blood supply. There are eligibility requirements donors must meet including being in good health and avoiding fatty foods before donating. After donating, donors should drink fluids, avoid strenuous activity, and apply pressure if bleeding occurs at the needle site.