Calcium, vitamin D , and magnesium should be carefully balanced. Calcium without enough Vitamin D leads to cramps and kidney stones. Excess vitamin D can be toxic. Excess magnesium leads to loose stools and insufficient magnesium leads to constipation. Vitamin D is stored in the liver and thus is slow acting; slow acting calcium and magnesium help reach a steady equilibrium. Some careful experimentation over time is necessary to get the proportions right. Combination pills are distinctly unhelpful as the proportions do not match the need.