Caffeine Can Help Lightheadedness
Some people feel lightheaded when giving blood. If that's happened to you, you may want to try drinking coffee beforehand. Researchers at Ohio University report that those who drank about two cups of coffee before donating were significantly less likely to feel woozy than those who had no caffeine in their systems. Caffeine can raise blood pressure and heart rate, however, so this method may not be for everyone.