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Should Calcium Supplements Be Taken Once or Twice a Day?


Updated October 08, 2008

Question: Should Calcium Supplements Be Taken Once or Twice a Day?

A question from a reader: I’m a 56-year-old woman, and I take calcium supplements. I have heard various opinions about how and when to take them. Should I take 1200 mg at once, or 600 in the morning and 600 at night? Is there anything I should not take calcium with? Thanks for the info.


According to the National Osteoporosis Foundation, adults 50 and over need 1,200 mg of calcium and 800 to 1,000 IU of vitamin D3 daily. The preferred source of calcium is calcium-rich foods, such as dairy products, tofu, certain green vegetables and foods that have been fortified with calcium.

If you are using a calcium supplement, the absorption of calcium depends on the total amount of calcium you take at one time and whether you take the calcium with food or on an empty stomach. When using a calcium supplement, the percent of calcium absorbed decreases as the amount of calcium in the supplement increases. Therefore, since you are using a 1200 mg calcium supplement, you should take 600 mg twice a day instead of 1200 mg calcium at one time.

Calcium and Medication Interactions

Several prescription and over-the-counter medications have the potential to interact with calcium supplements. If you are taking medications, talk with your healthcare provider or pharmacist about possible drug interactions. Also, medications that need to be taken on an empty stomach should not be taken at the same time as your calcium supplement.

Foods That Interfere with Calcium Absorption

There are several foods that can interfere with your body's ability to use calcium, including:

  • Foods with high amounts of oxalate such as spinach, rhubarb and beet greens
  • Foods with high amounts of phytate such as pinto beans, navy beans and peas
  • Caffeine
  • 100% wheat bran

If you consume any of these foods, you can take your calcium supplement two or more hours before or after eating them.

More Information from Dr. Mike:

Additional Resources

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  6. Calcium Supplements - Should I Take a Calcium Supplement Once or Twice a Day

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