4 Great Reasons to Donate Blood (hint… it’ll improve your health) One: You can help someone whose life may depend on your donation. Most blood banks, like Blood Works Northwest in the Puget Sound, are always needing more blood and they can store the blood for about 42 days. Approximately 25% of Americans will need a blood transfusion at some point in their lives. You or a loved one may be one of them. Two: There is some evidence to show that donating blood can lower your risk