The simplest reason to donate blood is also the best: when you donate blood, you can save someone else's life. For people who need additional motivations, there are lots of other reasons to consider giving a blood donation, and to make a regular habit of donating. It is important to keep in mind that there is no synthetic replacement for whole blood, and that whole blood and a number of blood products are derived exclusively from donors, which means that a blood donation provides the medical community with a resource which would otherwise be unobtainable.
According to statistics maintained by the American Red Cross, someone in the United States needs blood every two seconds. Maintaining the blood supply to meet the needs for blood is a tough task, because blood has a short shelf life, and shortages are a recurring problem. Blood is used in surgery, emergency medical treatment, and the treatment and management of a number of diseases. The need for blood, in other words, never stops.
People who are interested in community service and want to contribute to their communities may want to donate blood as a way of getting involved in the community and promoting community welfare. Patients who have benefited from blood transfusions may want to consider giving blood as an expression of appreciation for the anonymous donor or donors who benefited them, and giving blood also ensures that there will be blood when the donor, a friend, or a family member needs it. People who would prefer to know where their donation is going can engage in directed donation, banking blood in advance of a surgical procedure for themselves or giving blood to a friend or family member in need.
Another reason to donate blood is that it comes with a free mini-physical. While people should not donate blood if they think they are unhealthy, or use blood donation as a free STI screening, giving blood provides people with an opportunity to be seen by a nurse who will take vital signs and provide basic information about the donor's health, and if problems are identified when the blood is screened, the donor will be notified. This screening process is done to confirm that the blood will be safe to use, but it also benefits the donor.
People with type O negative blood are in especially high demand as donors, because their blood can be infused into anyone. People with rare blood types may also be appreciated as donors, as their gift of rare blood can help someone with the same blood type who may be in need. However, all blood types are equally welcome at blood banks and blood drives.