Taking a multivitamin and calcium supplement can be done at the same time with certain precautions. If your multivitamin contains calcium, this can reduce the absorption of calcium from your calcium supplement because the more calcium you take at one time, the less your body absorbs. Iron, zinc and calcium can interfere with each other's absorption if the concentration of any particular mineral is too high.
Calcium absorption is concentration-limited. The higher the concentration, the less you will absorb. The Linus Pauling Institute at Oregon State University says you should limit your calcium intake to less than 500mg at one time. If your calcium supplement and the amount of calcium in your multivitamin add up to 500mg or more, don't take them together. Your body will absorb less calcium than it would if you take each separately.
Read the label on your supplement for the amount of elemental calcium. This is the amount of calcium that is available for your body to absorb. According to American Bone Health, the amount of elemental calcium available in a multivitamin and calcium supplement aids you in determining how many tablets you need to take to meet your calcium need. Remember the closer the amount gets to 500mg, the less your body will absorb because this is the maximum amount of calcium your body can take in at one time.
Some multivitamins contain iron. Iron and calcium compete for absorption in your small intestine. According to the Linus Pauling Institute, you should take your iron supplements or iron-containing multivitamin at least two hours apart from your calcium supplement. This will increase your iron absorption.
Calcium may interfere with zinc absorption, especially in postmenopausal women. According to the Linus Pauling Institute, high calcium intakes lowered zinc absorption in postmenopausal females. Calcium supplements are concentrated doses of calcium and may limit how much zinc your body can absorb from your multivitamin. Take your multivitamin and calcium supplement at different meals or different times in the day to enhance absorption of both minerals.
Older Than 60
As you get older, your absorption of vitamin D, calcium, iron, zinc and magnesium decreases. Spacing out your multivitamin and calcium supplement increases your absorption of minerals and vitamins. According to Dr. Julian Whitaker of Stanford University, taking your multivitamin in split doses increases absorption because your body will take what it needs at the time and disregard the rest. To enhance absorption, split your multivitamin into two servings or purchase a multivitamin that is a multi-dose tablet, and take it separately from your calcium supplement.