What you need to know about magnesium is that 50% of the magnesium is in the bone, and only 1% is actually found in the blood, but the body works very hard to keep that 1% going in the blood. A lot of people have speculated or thought or touted that low magnesium levels aid or cause headaches. I don't know if that's necessarily true. I do believe that if you were drinking 8 ounces of water with a magnesium supplement, that could probably help you with your headaches even more than the magnesium itself. Most people in this country do not have any kind of issues taking any magnesium. So, you know, in terms of deficiencies, that's really not seen. You can take in plenty without any ill effects. But magnesium's critical for a lot of body functions, so you really want to make sure that you are eating your fruits and your vegetables and that kind of stuff, which is important you are taking a good multivitamin.