GrammieJan - While MagOx is inexpensive, it's also one of the hardest types of Magnesium supplement to absorb. It can be like flushing your money down the toilet when your body purges it unprocessed.
Try a Magnesium Glycinate or one of these other ones:
http://www.naturalnews.com/046401_ma...bsorption.html - pay attention to the benefits and side effect though. The citrate especially!
If a blood draw is showing that you're low - there's a very good chance that you're very low (but there's a good chance your doctor doesn't realize that - I have tons of pages of medical publications that back it up but most doctors are operating on 15 year old information. My GP told me that magnesium deficiency is "very rare" - it's not. It's considered the "new epidemic". At least your cardiologist is testing though.) - the 1% that's in the serum is tightly regulated because it's responsible for the relaxation part of the heart beat and other vital functions. If the blood runs low, it's pulled immediately from the tissues and cells. Blood serum tests are thought to give an incomplete picture because of this and because the "normal" range is thought to be too high for the low end. Your reserves can be depleted but a mag test might even show low normal or even mid-range normal. The better tests are to test the levels in cells or tissue but those test are expensive and not widely available.
I supplement with the Mag/Glycinate from Pure Encapsulations - my chiropractor carries it, Epsom Salt foot soaks and diet - dark leafy greens, nuts, seeds (especially pumpkin seeds), fish, beans, whole grains, avocados, bananas, dried fruit, dark chocolate, etc - just to keep a low "normal" test result. Yogurt can be another one but I can't have milk. This regime manages muscle tremors, and problems with my nervous system (including heartbeat irregularities) and cognitive issues but if I fall off it for more than 2 days, I start to suffer - it starts with sudden motion sickness and deteriorates from there.
I'm glad you asked about the difference between the cocoa and cacao! I had thought that they were just different spellings of the same product, one being closer to the name of the plant from which it's derived. I can't have cocoa - it gives me migraines, but I may try the cacao though since most things that seem to bother me tend to be as a result of (over)processing.