03/18/2010 05:12 am ET | Updated May 25, 2011

It's National Blood Donor Month -- Learn How You Can Get Involved...

In the US, most blood centers have difficulty keeping any more than a three-day supply of blood for transfusions. This means that the blood you donated last month is long gone. The need for blood, platelets, and plasma is constant, but only three in every 100 Americans donate blood, coming together to donate 81 million units of blood annually. Baby boomers currently account for the most blood donations, but they are rapidly reaching the age when medications and health issues bar them from being able to donate. At the same time, they are the largest age cohort of the world population and require more donated blood for their own health, quickly using much of the supply they once supported themselves.