So what is the best method to check for a deficiency? I have a severe magnesium deficiency (urine load test is far better than a blood test to determine that by the way) that I have been getting weekly IV's for and that has helped with the Atrial Fibrilation and other heart symptoms but I still require meds and it does bother me pretty much daily... I still require occasional cardioversions so any help like this would be great.