What Vitamins Should Duodenal Switch Patients Take?

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The Duodenal Switch (DS) is both a restrictive and a malabsorptive surgery. The smaller stomach helps patients eat less food and the rearrangement of the intestine causes them not to absorb all the calories that they do eat. The rearrangement of the intestine also causes them not to absorb vitamins and minerals well. They generally need to take even more vitamins than gastric bypass patients do.
The vitamins you need will probably vary based on your individual needs and the results of your blood tests, but here are the basics that the American Society for Metabolic and Bariatric Surgery recommends for all DS patients:
  • An adult multivitamin, containing 100% of the recommended daily allowance (RDA) of at least 2/3 of all nutrients, including 18 mg iron and minerals like zinc and selenium, twice daily
  • 1800 mg to 2400 mg calcium citrate (not calcium carbonate or tricalcium phosphate), divided into three or four doses of about 600 mg each, taken at least two hours apart
  • An additional 18 mg to 27 mg iron for menstruating women
  • 10,000 IU vitamin A
  • 2000 IU vitamin D
  • 300 mcg vitamin K
  • B-50 complex is optional
  • Other vitamin and mineral supplements may be needed, based on the results of your blood tests; for instance, some DS patients need to take additional B12
Notice that the ASMBS recommends a multivitamin made for adults. If you prefer a chewable multivitamin, or if your surgeon or dietician recommends chewable vitamins, you can purchase chewable vitamins made for adults. Children’s vitamins usually lack some important nutrients that DS folks need. You can purchase special bariatric vitamins if you wish, but these aren’t necessary. Just make sure your multivitamin has 100% of the RDA of most nutrients.
The ASMBS also recommends calcium citrate over other forms of calcium, including calcium carbonate. That’s because calcium citrate is absorbed more easily and because it doesn’t increase the risk of kidney stones. Calcium blocks the absorption of iron, so take your calcium at least two hours away from your iron supplement. If there’s iron in your multivitamins and you want to absorb that iron, take your calcium at least two hours away from your multivitamins, too.
Notice that the ASMBS recommends both men and women take a multivitamin that contains iron. If your multivitamin doesn’t have iron, or if you menstruate, you’ll need extra iron. There are many different types of iron from which you can choose. I like carbonyl iron because it’s less like to cause constipation or an upset stomach than some other forms of iron, like ferrous sulfate.
The ASMBS recommends using a retinol form of vitamin A, like retinol palmitate or retinol acetate, rather than beta carotene because they are absorbed more easily. Vitamin A often comes in soft gels filled with oil, but since DS folks malabsorb fats, they don’t absorb vitamins in oil well. Use dry vitamin A instead.
When it comes to vitamin D, it’s important to know that there are two forms of vitamin D, D2 and D3. According to the Vitamin D Council, D3 is much more effective for everyone, not just weight loss surgery patients. As with vitamin A, vitamin D3 sometimes comes in soft gels filled with oil, but DS folks absorb dry D3 better. Note that some post ops need significantly more vitamin D than recommended by the ASMBS to maintain a good level and you should adjust your dose as needed based on your blood tests.
As with vitamins A and D, vitamin K should be taking in dry form. The ASMBS recommends vitamin K be taken with caution by patients receiving coagulation therapy, which includes drugs like Warfarin and Coumadin. Talk to your doctor about whether or not to take vitamin K if you are on one of these medications.
Talk to your bariatric surgeon or a registered dietician with experience treating DS patients if you have questions about what vitamins you should take.
This article was written by Kelly Morris for Bariatric Foodie.


  1. The blog was absolutely fantastic! Lot of great information which can be helpful in some or the other way.

    Duodenal switch

  2. Thanks for sharing, perfect timing after my Duodenal Switch surgery 4months ago, I travel in Thailand just for my Duodenal Switch surgery and placidway help me to settled an appointment.

  3. I had no idea that duodenal switch patients should be taking vitamins to supplement their nutrition. I have a friend who is considering this surgery as a weight loss option. Would a recipient of this surgery need to take vitamins as a long term supplement? http://www.weightlosssurgeon.com/weight-loss-surgery/weight-loss-surgery-types/duodenal-switch-biliopancreatic-diversion