The short answer
Yes, and separate the doses. Cholestyramine can block absorption of vitamin D taken with it, so take vitamin D at least 1 hour before or 4 to 6 hours after the resin, the label's spacing rule for other oral medicines. Whether cholestyramine actually lowers vitamin D levels is mixed: in a study of 268 men, vitamin D metabolites in the 124 prescribed 24 g a day for 7 to 10 years did not differ significantly from those in the 144 assigned placebo, and a 24-week adult study also found no change, but in children taking 8 g a day for a year, 25-hydroxyvitamin D fell. The label suggests considering water-miscible forms with long-term use. A clinician can decide whether a 25-hydroxyvitamin D test would help assess your vitamin D status.
What this answer covers
Vitamin D2 (ergocalciferol) or D3 (cholecalciferol) supplements and multivitamins taken with cholestyramine resin powder for oral suspension. Calcifediol and other prescription vitamin D metabolites are outside this answer.
- Supplement or preparation
- vitamin D
- Medication ingredient
- cholestyramine resin
What the label says
The cholestyramine label states that the resin may prevent absorption of fat-soluble vitamins such as A, D, E and K, that water-miscible or parenteral forms should be considered with long-term use, and lists vitamin D deficiency and osteoporosis among less frequent adverse reactions. Its only spacing rule is for other drugs: at least 1 hour before or 4 to 6 hours after the resin, or as long an interval as possible.
Long-term adult studies found no change
In a study of 268 men followed for 7 to 10 years, vitamin D metabolites measured at the final visit did not differ significantly between 124 men prescribed 24 g of cholestyramine daily and 144 assigned placebo. A separate 24-week study of 24 g daily, alone or with pravastatin, found no change in vitamin D metabolites or parathyroid hormone. These studies assessed vitamin status during medication treatment; they did not establish a vitamin D supplement dose.
Children and people with bowel disease
In a 1-year placebo-controlled study of children aged 6 to 11 taking 8 g a day, mean 25-hydroxyvitamin D fell and the authors advised considering vitamin D supplements. The report of osteomalacia reviewed here was in a woman with Crohn disease and an ileal resection, conditions that limit vitamin D absorption on their own; she improved on calcifediol, a prescription metabolite rather than ordinary vitamin D. These findings support discussing vitamin D assessment and supplementation with the prescriber when treating children or people with malabsorption.
How the interference works and why timing matters
Bile-salt micelles help vitamin D absorption. In rats, cholestyramine reduced absorption of labelled vitamin D3 by binding bile salts and disrupting those micelles, while calcium absorption was unaffected. Separating the doses follows the label's general rule for other oral medicines, but no vitamin D-specific timing trial shows that spacing fully prevents the absorption problem.
Practical approach
Take vitamin D at least 1 hour before or 4 to 6 hours after cholestyramine, following the label's general spacing rule for other oral medicines. Extra vitamin D is not automatic. Ask the prescriber whether your treatment duration, age, diet or a bowel or liver condition warrants assessment of vitamin D status. For adults, the upper intake level is 4,000 IU daily unless a prescriber directs otherwise; excess vitamin D can raise blood calcium.
Evidence and practical considerations
Absorption & effectiveness
Cholestyramine can block vitamin D absorption in the gut, but vitamin D metabolite levels did not differ from placebo at the final visit of a 7- to 10-year study in men and did not change during a 24-week adult study, while 25-hydroxyvitamin D fell in children on 8 g daily; the osteomalacia case reviewed was confounded by ileal resection.
- Exact scope
- Vitamin D2 and D3 supplements; calcifediol differs. with Cholestyramine resin powder for oral suspension (generic products, Questran and Prevalite) at any dose; the interaction happens in the gut because the resin is not absorbed.
- Medication form and route
- oral medication; oral supplement
What remains uncertain
- Adult data are end-of-trial or short-term measurements; the pediatric decrease lacks magnitude; mechanism data are from rats.
Factors that may matter: Age (children versus adults); Underlying bowel or liver disease; Duration and dose of cholestyramine; Sun exposure and dietary vitamin D.
Read the supporting source summaries
Source 1: current product label
dailymed.nlm.nih.gov · Source check Sep 22, 2026
Population: People prescribed cholestyramine resin
The resin may prevent absorption of fat-soluble vitamins such as A, D, E and K; supplementation with water-miscible or parenteral forms should be considered with long-term use. Vitamin D deficiency and osteoporosis are listed among less frequent adverse reactions. The label tells patients to take other drugs at least 1 hour before or 4 to 6 hours after cholestyramine, or at as great an interval as possible; it gives no vitamin-specific interval.
How this applies: Exact cholestyramine resin (RxCUI 2447) as oral powder for suspension; the innovator Questran label captured in this batch carries the same folate, vitamin K, fat-soluble vitamin and spacing wording.
No frequency, dose or vitamin-specific interval is given.
Source 2: original human study
pubmed.ncbi.nlm.nih.gov · Source check Sep 22, 2026
Population: Two hundred and sixty-eight men, 124 on cholestyramine and 144 on placebo.
No differences between cholestyramine and placebo in calcifediol (62.6 versus 63.4 nmol/L), 25-hydroxyvitamin D2, calcitriol, calcium, phosphorus or albumin.
How this applies: Strongest long-term evidence: vitamin D metabolites at the final visit did not differ significantly in adult men assigned cholestyramine or placebo for 7 to 10 years.
Single end-of-trial measurement; results limited to men aged 42 to 68; abstract truncated before the parathyroid hormone result.
Source 3: original human study
pubmed.ncbi.nlm.nih.gov · Source check Sep 22, 2026
Population: Forty hypercholesterolemic adults, mean age 58.
Parathyroid hormone and the vitamin D metabolites 1,25-dihydroxyvitamin D3 and 25-hydroxyvitamin D3 did not change during treatment.
How this applies: Short-term adult data showing no change in vitamin D metabolites.
Forty patients across several arms, so few on cholestyramine alone; 24 weeks; abstract only.
Source 4: original human study
pubmed.ncbi.nlm.nih.gov · Source check Sep 22, 2026
Population: Ninety-six children aged 6 to 11 years, 36 randomized to cholestyramine.
Mean 25-hydroxyvitamin D decreased in the cholestyramine group; the authors concluded vitamin D supplements should be considered.
How this applies: The one controlled study showing a fall in vitamin D status, in children at a modest dose.
Magnitude not given in the abstract; many withdrawals; children only.
Source 5: case report
pubmed.ncbi.nlm.nih.gov · Source check Sep 22, 2026
Population: One woman with Crohn disease and ileal resection.
Severe histological osteomalacia developed; calcifediol produced marked biochemical, radiological and histological improvement after 6 months. The authors suggested cholestyramine precipitated the osteomalacia and advised routine vitamin D supplementation with long-term cholestyramine.
How this applies: A confounded case: the bowel disease and surgery limit attribution to cholestyramine, and the corrective product differs from ordinary vitamin D supplements.
One patient with ileal resection and Crohn disease, both of which impair vitamin D absorption on their own; the treatment was calcifediol, not vitamin D2 or D3.
Source 6: animal study
pubmed.ncbi.nlm.nih.gov · Source check Sep 22, 2026
Population: Rats.
Cholestyramine reduced absorption of vitamin D3 but not of radiocalcium; in vitro data suggested the effect came from binding bile salts and disrupting the micelles that carry vitamin D.
How this applies: Mechanism only: shows how the resin can block vitamin D absorption when both are present in the gut.
Rat experiment at steatorrhoea-producing doses; not a human study.
Research assessment: · Open full citations ↗
Timing & monitoring
Take vitamin D at least 1 hour before or 4 to 6 hours after cholestyramine, the label's general interval for oral drugs; the micelle mechanism supports separating the doses, and the adult upper limit is 4,000 IU daily.
- Exact scope
- Vitamin D2 and D3 supplements at any dose. with Cholestyramine resin powder for oral suspension (generic products, Questran and Prevalite) at any dose; the interaction happens in the gut because the resin is not absorbed.
- Medication form and route
- oral medication; oral supplement
What remains uncertain
- No vitamin D-specific interval has been tested; the label rule is written for other drugs.
Factors that may matter: Time between doses; Vitamin D dose; Other medicines taken with the resin.
Read the supporting source summaries
Source 1: current product label
dailymed.nlm.nih.gov · Source check Sep 22, 2026
Population: People prescribed cholestyramine resin
The resin may prevent absorption of fat-soluble vitamins such as A, D, E and K; supplementation with water-miscible or parenteral forms should be considered with long-term use. Vitamin D deficiency and osteoporosis are listed among less frequent adverse reactions. The label tells patients to take other drugs at least 1 hour before or 4 to 6 hours after cholestyramine, or at as great an interval as possible; it gives no vitamin-specific interval.
How this applies: Exact cholestyramine resin (RxCUI 2447) as oral powder for suspension; the innovator Questran label captured in this batch carries the same folate, vitamin K, fat-soluble vitamin and spacing wording.
No frequency, dose or vitamin-specific interval is given.
Source 2: animal study
pubmed.ncbi.nlm.nih.gov · Source check Sep 22, 2026
Population: Rats.
Cholestyramine reduced absorption of vitamin D3 but not of radiocalcium; in vitro data suggested the effect came from binding bile salts and disrupting the micelles that carry vitamin D.
How this applies: Mechanism only: shows how the resin can block vitamin D absorption when both are present in the gut.
Rat experiment at steatorrhoea-producing doses; not a human study.
Source 3: federal nutrient fact sheet
ods.od.nih.gov · Source check Sep 22, 2026
Population: General population; no cholestyramine co-use data
Vitamin D2 and D3 are inert until hydroxylated to 25-hydroxyvitamin D, the status marker; deficiency causes osteomalacia in adults and can occur when absorption from the digestive tract is inadequate. The Tolerable Upper Intake Level is 4,000 IU (100 mcg) daily for adults and excess vitamin D causes hypercalcemia. The interactions section names orlistat, statins, steroids and thiazides; cholestyramine is not mentioned.
How this applies: Defines the supplement forms, the status test, the upper limit and deficiency signs.
General nutrient guidance; no cholestyramine data.
Research assessment: · Open full citations ↗
Review and change history
- Publication status
- Published research summary
- Clinical review
- Not yet recorded
| Date | Update |
|---|---|
| Editorial update | |
| Source-checked release edit clarified study design, exact evidence scope and practical wording. This research edit does not constitute clinical approval. | |
| Research summary published | |
| Article prepared | |
| Prepared exact cholestyramine resin and Vitamin D article from inspected current labeling and original sources, with uncertainty stated. |
Article revision: a3809ea9417e07f8
This guide brings together the evidence records used by our interaction checker. Each finding retains its own preparation limits, research date, and source summaries.
Full citations require verification. Reading this answer and the source summaries does not.
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