Giving Blood

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Hello... I find I have a really hard time after giving blood for like 2 - 3 days. I feel cruddy and want to eat. They say you can burn like 800 calories and lose a pound when giving blood, but I usually end up eating back way more than that since I feel so rotten.

Thing is that I want to get in a habit of giving blood regularly. I am type O positive which is in high demand. I'm in good health and can earn points with my wellness program at work for doing it. Plus I like saving lives.

Does any one else give blood regularly and, if so, how do you beat the blahs without going overboard on eating? I am almost 5'4" and around 120 lb. Thanks!