Do Calcium and Vitamin D Need to be Taken Together?

I’ve received this question twice in the past week, so thought I’d turn it into a post in case other people are wondering the same thing:

“Do you have any view on whether calcium and Vitamin D supplements should be taken at the same time to ensure they are absorbed properly? This seems to be the reason that calcium and Vitamin D are often sold in the same pill. Alternatively, if you aim to get Vitamin D from sunshine, should you wait to take the calcium supplement at that point of the day?”

There is no need to take vitamin D (or get sun) at the same time as you eat calcium. The vitamin D that you eat needs to be absorbed into your blood and then taken to the liver to be modified into a circulating, storage form of vitamin D known as 25(OH)D. Then, when your body senses that you need to absorb more calcium, the kidney further modifies the 25(OH)D into the hormone calcitriol. Calcitriol then increases calcium absorption. Vitamin D ingestion at a single meal will not have an effect on calcium absorption at that meal.


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5 Responses to “Do Calcium and Vitamin D Need to be Taken Together?”

  1. Dan Says:

    I’ve become very circumspect about recommending calcium supplementation because of a number of recent studies suggesting potential harm – mainly heart attacks and strokes – from calcium supplements. A pair of meta-analyses of randomized trials in the BMJ suggested this, and was followed by a couple of observational studies in Heart and Archives of Internal Medicine (now called JAMA Internal Medicine). Unless a patient has known osteoporosis, or is on systemic long-term steroids, I would not prescribe calcium for bone health.

  2. Jack Norris RD Says:


    Did you see this Tufts study looking directly at calcification of the arteries?

    Additionally, I have reviewed a number of the studies associating calcium with heart disease and they link them for calcium intakes above 1400 mg, an amount no vegan would get by taking 250-500 mg per day.

    You might want to check out my article on calcium and vegan diets:

  3. Andreas Says:

    Very well said Jack. Couldn’t have said it better myself. However I would have added that calcitriol enhances absorption of other minerals, like Iron, magnesium, cobalt, etc..


  4. Dedra Lapidus Says:

    I take calcium strictly because I need magnesium and I’ve heard you need the calcium to balance it out or your colon won’t absorb water. Is that true?

  5. Jack Norris RD Says:


    I seriously doubt that.

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