Calcium and magnesium are both present in large amounts in your body, especially in your bones. They're both found in foods and are also available as dietary supplements. The Food and Nutrition Board of the Institute of Medicine has set tolerable upper intake levels, or ULs, for both minerals.
The UL for calcium is 2,500 milligrams per day and includes the intake from food and dietary supplements. The IOM warns that the adverse effects of consuming too much calcium include an increased risk of kidney stones, high levels of calcium in the blood, pH problems, and kidney disease. The UL for magnesium is 350 milligrams per day. Exceeding the UL for magnesium can cause diarrhea. The UL of 350 milligrams only includes magnesium in supplement form, according to the IOM. You should speak to your healthcare provider before taking dietary supplements.