Quick answer

Ask your pharmacist or doctor before combining. The cholestyramine label and MedlinePlus document 2 supplements for bile acid sequestrants: vitamin D and vitamin K. MedlinePlus names vitamins A and E too, so the issue is the fat-soluble vitamins as a group. NIH says the clinical importance of the vitamin K effect is not clear.^1,2,3

Key facts

MedlinePlus says cholestyramine is used to lower cholesterol and works by binding bile acids in the intestines.⁴
The label says cholestyramine may prevent the absorption of the fat-soluble vitamins A, D, E and K.¹
The label lists low vitamin A, D and K among its less frequent adverse reactions, and links long-term use to a bleeding tendency from low vitamin K.^1,5
MedlinePlus lists vitamin A, D, E and K supplements among the nonprescription products that may interact with cholestyramine.²
NIH says vitamin K status should be monitored in people who take these medicines, especially over many years.³

What are bile acid sequestrants used for?

Bile acid sequestrants are medicines that lower cholesterol. MedlinePlus describes cholestyramine, a powder mixed with liquid, as one that binds bile acids in the intestines so they leave the body. NIH's vitamin K sheet names cholestyramine and colestipol as examples. This page uses the cholestyramine page as the example for the class.^4,6

For these medicines, the label and NIH say the group affected is the fat-soluble vitamins.^1,3

How do bile acid sequestrants affect vitamin D and vitamin K?

For vitamin D, the label lists low vitamin D among the effects of long-term use, and MedlinePlus lists vitamin D supplements among the products that interact.^1,2

Ask your pharmacist or doctor first

Bile acid sequestrants such as cholestyramine can block the absorption of fat-soluble vitamins, including vitamin D. The cholestyramine label lists low vitamin D among the effects of long-term use, and MedlinePlus lists vitamin D supplements among the products that interact with it.^1,2

On the medicine's label

Vitamin K has the most detail. The label links years of use to a bleeding tendency from low vitamin K. NIH adds two cautions of its own: the clinical significance of the effect is not clear, and vitamin K status should be monitored in people who use these medicines for many years.^3,5

Ask your pharmacist or doctor first

Bile acid sequestrants such as cholestyramine and colestipol can reduce the absorption of vitamin K and the other fat-soluble vitamins, especially over years of use. The cholestyramine label links long-term use to a bleeding tendency caused by low vitamin K, and MedlinePlus lists vitamin K supplements among the products that interact with it.^3,5,6,7

On the medicine's label

Do vitamins A and E belong on the list too?

The label names vitamins A, D, E and K as a group, and MedlinePlus lists supplements of all four. So the pattern is wider than the two entries above. Ask about any multivitamin or single supplement that carries vitamin A or vitamin E.^1,2

Why are these entries tagged ask first and not avoid?

This interaction differs from most, because the label does not only warn about taking a supplement. The cholestyramine label itself says these vitamins should be considered as supplements during long-term use. Whether any supplement is needed, in what form and how much, is a decision for the prescriber, which is why both entries carry ask first. Both are on the label.¹

Does a bile acid sequestrant change when other medicines are taken?

MedlinePlus gives a schedule for taking other medicines before or after cholestyramine, and asks people to tell their doctor and pharmacist about every vitamin, nutritional supplement and herbal product. Ask your pharmacist whether the schedule covers your supplements, and what it is for each one.⁴

What should you ask your pharmacist about bile acid sequestrants and vitamins?

Which fat-soluble vitamins are in my multivitamin or single supplements: A, D, E or K?
Have my vitamin D and vitamin K status been checked, especially after years of use?
Does the schedule for my other medicines cover my supplements?
Which of my medicines is a bile acid sequestrant, such as cholestyramine or colestipol?
Should anything change if I stop or switch this medicine?

Questions people ask

What vitamins should not be taken with bile acid sequestrants?

The label and MedlinePlus name vitamins A, D, E and K, which the medicine may stop the body from absorbing. The label also says these vitamins should be considered as supplements during long-term use, so ask your prescriber before changing any of them.^1,2

Does cholestyramine affect vitamin D?

The cholestyramine label lists low vitamin D among the effects of long-term use, and MedlinePlus lists vitamin D supplements among the products that interact. Ask your pharmacist about your own case.^1,2

Do bile acid sequestrants lower vitamin K?

They can reduce vitamin K absorption, especially over years, and the label links long-term use to a bleeding tendency from low vitamin K. NIH says the clinical significance is not clear and that vitamin K status should be monitored.^3,5,6

What supplements interact with bile acid sequestrants?

Vitamin D and vitamin K are documented here, and MedlinePlus also lists vitamins A and E. For any other supplement the sources checked do not address it. That is not a finding either way, so ask your pharmacist.²

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Sources

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.