I was taking magnesium oxide originally which was my problem. Poor abosrption.

I think there are many good types and brands out there.

I take Source Naturals Magnesium Malate 425 mg per day. I also use Ancient Minerals magnesium oil once a day. I exercise daily for about an hour and therefore take a bit more than the RDA to compensate for losses occuring from exercise/sweating , etc.