Giving the cells in your body the optimal amount of magnesium isn't as easy as swallowing a supplement or two every day. Quantity alone is no guarantee, and an overload could be harmful. For a nutrient like vitamin C, to give an example, you can dose yourself into a case of diarrhea, but that's about the only side effect you'll suffer. Big doses of magnesium, particularly magnesium oxide, also causes diarrhea, which makes it a good short term treatment for chronic constipation, but diarrhea is not a benign consequence. Taking too much could be dangerous, especially if your blood's concentration already is high, as can happen when certain kidney problems prevent the mineral from being excreted. No one with seriously diminished kidney function should take magnesium supplements without careful medical supervision.
Blood tests are the best way to determine your true need and track the effectiveness of supplements. Don't rely on standard blood serum measurements. They can be misleading and will often fail to detect a deficiency. A much better gauge is the mineral's concentration within red blood cells. I've found that the optimum dosage for magnesium-related health problems typically brings the red blood cell reading to a point slightly above the middle of the "normal" range. For most people this usually translates into a daily dosage of 400-1,000 mg.
To reach the ideal point, some formulations work better than others. Magnesium oxide, the type most frequently found in mineral supplements, does easily raise the standard blood serum level, but other forms deliver the nutrient to tissue cells more successfully. My favorite is magnesium orotate, which, although once difficult to find, is now beginning to be found in health food stores. Other good forms are magnesium taurate, magnesium chloride, magnesium glycinate and magnesiumm aspartate.
As an alternative, go soak your feet --- and the rest of your body. Epsom salts are known chemically as magnesium sulfate, and your skin will absorb as much of the mineral as you need. Drawing a bath and pouring in some Epsom salts can be as nourishing as it is relaxing.