It's opposite of what most people with AF experience, but I can't tolerate any magnesium in any form. It makes things bad, and causes severe muscle cramps at night.
Calcium on the other hand, I seem to need. I take about 1 gram daily. If I back off on the calcium I also get muscle cramps. Not sure why. My diet is extremely low in Magnesium to begin with. There must be a mineral metabolism issue in the body.