You're tired because you have 1 pint less of blood after donating. It takes a while for your body to build the blood back up. There are no health benefits to you unless you have a rare health condition, but there are some pretty great benefits to the health of the person who needs your blood.
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there are no health benefits (unless you suffer from polycythemia ) but there are no severe adverse reactions, you can donate blood safely. you get tired from the sudden drop in red cell mass, the body quickly adjusts with increased production of red cells & they always give you a drink to compensate for fluid loss.
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I can't think of any health benefits, but that doesn't mean there isn't any. You are tired because your blood has significantly less ability to carry oxygen now because it has fewer red blood cells to do the same job. Without enough oxygen you can't perform at your regular level.
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I don't know of any health benefits, besides feeling good about yourself afterward. You are tired because you just lost 1 pint of blood. This makes your cells get less oxygen, which in turn makes you feel tired.