Magnesium deficiency is very common in the general US population. Not only is our daily intake low, but we eat a diet which increases the demand for magnesium. And unfortunately, urinary magnesium loss can be increased by many factors, both physical and emotional. Magnesium loss increases in the presence of certain hormones. Stress can greatly increase magnesium loss. Even loud noises can cause magnesium loss. One article on the web goes so far as to say that that almost everyone is the United States is at least marginally deficient in magnesium. So there is an excellent chance that a person with fibromyalgia has a magnesium deficiency.