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If you need to take a multivitamin, you'll want to take it in a way that maximizes absorption of its nutrients (i.e., essential vitamins and minerals) but is convenient enough so that you don't skip taking it. For many people, breakfast is the most convenient time to take a multivitamin, but if your breakfast does not include significant amounts of fats or oils, you won't get the best absorption of vitamin D and other fat soluble vitamins -- A, E, and K. In that case, take your multivitamin with whichever meal contains the most fats and oils. Taking your multivitamin with a meal may also reduce stomach upset or nausea that can occur with these supplements.

If you take separate supplements providing large amounts of vitamins or minerals, be aware that these can compete with the generally smaller amounts of similar nutrients in your multivitamin. For example, if you take a separate calcium supplement, take it at a different time of day than your multivitamin because the large amount of calcium will reduce absorption of minerals in your multivitamin, such as magnesium, iron, copper and zinc. Similarly, if you take a separate supplement with vitamin D, A, E, or K, take it at a different time of day than your multivitamin because it may reduce absorption of other fat-soluble vitamins in your multivitamin.

If you take a separate supplement with vitamin B12 (which 10 to 30% of older adults don't absorb well from foods), take it at least 6 hours apart from your multivitamin, because you can only absorb a small amount (about 1.5 mcg of B12) at a time. Taking small amounts of B12 twice daily is a good strategy to boost B-12 levels if needed and may be better than taking a large dose once a day.

Be aware that the calcium and/or magnesium in multivitamins may interfere with the absorption of certain medications, such as antibiotics, statins, and thyroid hormones. So, take them at a different time of day than your multivitamin.

When choosing a multivitamin, it's generally best to go with one that provides up to the daily requirement of each nutrient. Many multivitamins provide much more than you need, and this can potentially have negative effects. Check our Top Picks in our Multivitamin Supplements Review.

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August 22, 2019

My husband takes 500 mg of calcium with 500 IU of D and 250 mg of magnesium. It's a food based product from Rainbow Light and can be taken with or without meals. He was taking it with dinner along with 100 mcg of Vitamin K2, but I moved it to breakfast (usually a protein shake/smoothie) when I read that Vitamin D might block the absorption of K2. Now I read on your site that one shouldn't take a separate calcium supplement with a multivitamin which he takes at breakfast, so now I don't know what to do. Should I have him take the K2 in the morning and the calcium/vitamin D/magnesium with dinner?
August 23, 2019

Hi Diane - You're correct. 500 mg is a lot of calcium to take as a supplement at one time and taking more would not be a good idea. Also, best to find another time of day to the the vitamin K2 than with the vitamin D if possible, but best that each be taken with a meal containing some oils.

Julia 22842
June 28, 2021

Should calcium and magnesium be taken together? Some sources recommend a 2 hr. separation, stating the calcium will block absorption of the magnesium and zinc. It is confusing when they are in a product together. Any input on this?
July 2, 2021

Please see the ConsumerTips section of the Magnesium Review for information about taking magnesium and calcium together as well as other minerals, including zinc

May 9, 2019

Why isn’t weight considered for RDA?
May 9, 2019

Hi Gerald -- As noted on our RDAs page, Recommended Daily Allowances are calculated to meet the sufficient nutrient requirements of nearly all (97% - 98%) healthy people. The calculations factor in the median height and weight for each gender/age category (see However, it's true that needs may be different in some circumstances. For example, individuals who are obese require larger doses of vitamin D from supplements to reach adequate levels (see, and nutrient requirements may be different for people with certain diseases or medical conditions.

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