Yes, timing matters. When to take a calcium supplement depends on:

• Type of calcium. Check the label to find out what type of calcium the supplement has. Take calcium citrate with or without food. Take calcium carbonate with food. The acid the stomach makes while eating helps the body absorb calcium carbonate.
• Total daily dose. It's best to take calcium in smaller doses. Smaller doses most often means 500 milligrams or less at a time. To take 1,000 mg of calcium a day, split it into two or more doses over the day.
• Other medicines. Calcium supplements and many prescription medicines do not mix well. This includes antibiotics, bisphosphonates and high blood pressure medicines. Ask a pharmacist or member of your health care team what medicines shouldn't be taken with calcium supplements.

For people who take calcium supplements and multivitamins, it's best to take them at different times of day. Calcium can affect how the body takes in the nutrients iron, zinc and magnesium.

And don't take a calcium supplement at the same time as a meal that's high in iron. Foods high in iron include lean meat and seafood, nuts, beans, vegetables, and grains that have iron added to them.

If you have any questions about the best time to take calcium supplements, ask your pharmacist or a member of your health care team.