i was told last year i had stage 4 COPD and was on oxygen all night and when ever i got up from a sitting position during the day. i had been reading about magnesium and COPD and decided to try the lowest dose i could find of magnesium. what i bought was magnesium 250 mg and started taking one pill each day two months ago. (if you take calcium/vitamin D supposed to separate the times you take them.) i have been amazed at the improvement. hope if others try it, they see the same improvement. God Bless!