I donated blood at the Red Cross yesterday, and now I'm wondering about some of the claims they make, and whether it's really worth my time to donate. They say that you save a life every time you donate blood, and that all units donated are used. I don't see how this is possible. Surely some must go to waste, especially if you're of a less desirable blood type. The shelf life is apparently a few months, so I could envision most of the blood sitting on the shelf just in case someone needs it, then being disposed down the line. I know that here in America it's very rare that someone cannot get blood, so that means that there must be excess, doesn't it?