The short answer
Timing, yes; a higher dose, usually not. The colesevelam label says it may decrease absorption of fat-soluble vitamins including vitamin D and tells people on oral vitamin supplements to take them at least 4 hours before colesevelam. In the adolescent trial the label relies on, fat-soluble vitamin levels did not differ from placebo, and a review of the adult trials found no clinically significant vitamin changes. People with malabsorption conditions are at higher risk, and a clinician can decide whether a 25-hydroxyvitamin D test would help assess your status. So take vitamin D 4 hours before colesevelam.
What this answer covers
Vitamin D2 (ergocalciferol) or D3 (cholecalciferol) supplements and multivitamins taken with colesevelam hydrochloride tablets or oral suspension.
- Supplement or preparation
- vitamin D
- Medication ingredient
- colesevelam
What the label says
The WELCHOL label warns that colesevelam may decrease absorption of fat-soluble vitamins A, D, E and K, that people with malabsorption syndromes are at increased risk, and that patients on oral vitamin supplements should take them at least 4 hours before colesevelam. It reports that in the adolescent study there were no significant effects on fat-soluble vitamin levels or clotting factors relative to placebo.
What the studies show
The pediatric study enrolled 194 children aged 10 to 17. It compared colesevelam with placebo for 8 weeks, followed by an 18-week open-label phase in which all participants received colesevelam. The label reports no significant effects on fat-soluble vitamin levels or clotting factors relative to placebo; this was not a 26-week placebo comparison. A review of the early adult trials reported no clinically significant vitamin changes, and a pediatric review called for longer studies of vitamin depletion. The evidence reviewed does not establish a routine need for extra vitamin D, and no study comparing vitamin D supplementation during colesevelam use was found.
Before, not after
Take vitamin D at least 4 hours before colesevelam, the direction the label specifies. In healthy volunteers, drugs swallowed with colesevelam lost exposure but showed no interaction when taken 4 hours beforehand, which is why the label uses that window. For example, vitamins with breakfast and colesevelam with a later meal can work if there is at least a 4-hour gap before every colesevelam dose and the timing fits your prescribed schedule.
Who should be tested
Ask the prescriber whether a malabsorption condition, prolonged colesevelam use or bone disease warrants checking vitamin D status. Vitamin D deficiency can cause bone pain and muscle weakness. 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
Colesevelam is labeled as possibly decreasing vitamin D absorption, with higher risk in malabsorption, but the controlled adolescent study behind the label found no significant effect on fat-soluble vitamin levels versus placebo and adult trial reviews report no clinically significant vitamin changes.
- Exact scope
- Vitamin D2 and D3 supplements. with Colesevelam hydrochloride tablets and powder for oral suspension (WELCHOL and generics), 3.75 g daily; the polymer is not absorbed, so any effect happens in the gut.
- Medication form and route
- oral medication; oral supplement
What remains uncertain
- Vitamin results are read from the label and reviews rather than primary abstracts; 6 to 26 weeks; no data in malabsorption or with supplements.
Factors that may matter: Underlying malabsorption; Duration of colesevelam use; Sun exposure and dietary vitamin D; Time between doses.
Read the supporting source summaries
Source 1: current product label
dailymed.nlm.nih.gov · Source check Sep 22, 2026
Population: People prescribed colesevelam
WELCHOL may decrease absorption of fat-soluble vitamins A, D, E and K; patients with malabsorption syndromes or otherwise susceptible to fat-soluble vitamin deficiency may be at increased risk. Patients on oral vitamin supplementation should take their vitamins at least 4 hours prior to WELCHOL. In the adolescent study there were no significant effects on fat-soluble vitamin levels or clotting factors relative to placebo.
How this applies: Exact colesevelam hydrochloride (RxCUI 141626) tablets and oral suspension; the vitamin instruction covers oral vitamin supplements as a group.
The label reports no adult vitamin D levels, no supplement dose and no interval for taking vitamins after colesevelam.
Source 2: original human study
pubmed.ncbi.nlm.nih.gov · Source check Sep 22, 2026
Population: One hundred and ninety-four children aged 10 to 17 years, 129 treated with colesevelam.
LDL-cholesterol fell 12.5 percent with 3.75 g daily versus placebo; the abstract reports lipid results and that adverse events were evaluated, but gives no vitamin values. The WELCHOL label (section 8.4) draws on this population for its statement that fat-soluble vitamin levels and clotting factors showed no significant effects relative to placebo.
How this applies: The controlled study behind the label's null fat-soluble vitamin statement; adolescents without malabsorption.
Vitamin outcomes are not in the abstract; the null vitamin statement is read from the label, not the paper; 26 weeks total.
Source 3: review of clinical trials
pubmed.ncbi.nlm.nih.gov · Source check Sep 22, 2026
Population: Adults with primary hypercholesterolemia in the early trials.
In humans colesevelam did not induce clinically significant changes in serum levels of vitamins, coagulation parameters or liver enzymes; it did not alter the pharmacokinetics of several co-administered drugs.
How this applies: Summarizes the adult trial vitamin data that the primary abstracts omit; medication-only exposure.
Narrative review read as an abstract; underlying vitamin data are not shown; trials lasted 6 to 24 weeks.
Source 4: clinical review
pmc.ncbi.nlm.nih.gov · Source check Sep 22, 2026
Population: Children and adolescents with heterozygous familial hypercholesterolemia.
Colesevelam may decrease absorption of some medications such as multivitamins and should be given at least four hours after them; absorption of fat-soluble vitamins may be decreased; the authors call for further trials on long-term complications such as fat-soluble vitamin depletion. They suggest giving colesevelam with dinner, or split between lunch and dinner, when vitamins are taken at breakfast.
How this applies: Full-text review confirming the label's timing direction and the absence of long-term vitamin data.
Review, not original data; its four-hour advice restates the label.
Research assessment: · Open full citations ↗
Timing & monitoring
Take oral vitamin D at least 4 hours before colesevelam, as the label directs for oral vitamin supplements; the 4-hours-before window eliminated interactions for tested drugs, and no interval after colesevelam is labeled.
- Exact scope
- Vitamin D2 and D3 supplements at any dose; adult upper limit 4,000 IU daily. with Colesevelam hydrochloride tablets and powder for oral suspension (WELCHOL and generics), 3.75 g daily; the polymer is not absorbed, so any effect happens in the gut.
- Medication form and route
- oral medication; oral supplement
What remains uncertain
- The label instruction is class-wide for vitamins; the interval evidence comes from prescription drugs, not vitamin D.
Factors that may matter: Time between doses; Vitamin D dose; Other medicines taken with colesevelam.
Read the supporting source summaries
Source 1: current product label
dailymed.nlm.nih.gov · Source check Sep 22, 2026
Population: People prescribed colesevelam
WELCHOL may decrease absorption of fat-soluble vitamins A, D, E and K; patients with malabsorption syndromes or otherwise susceptible to fat-soluble vitamin deficiency may be at increased risk. Patients on oral vitamin supplementation should take their vitamins at least 4 hours prior to WELCHOL. In the adolescent study there were no significant effects on fat-soluble vitamin levels or clotting factors relative to placebo.
How this applies: Exact colesevelam hydrochloride (RxCUI 141626) tablets and oral suspension; the vitamin instruction covers oral vitamin supplements as a group.
The label reports no adult vitamin D levels, no supplement dose and no interval for taking vitamins after colesevelam.
Source 2: original human study
pubmed.ncbi.nlm.nih.gov · Source check Sep 22, 2026
Population: Healthy adult volunteers in six open-label randomized studies.
Concomitant colesevelam lowered exposure to glyburide, levothyroxine and ethinyl estradiol and the peak of repaglinide and norethindrone; when the drug was taken 4 hours before colesevelam no interaction was observed, and the authors concluded a 4-hour window appears sufficient.
How this applies: Explains the label's 4-hours-before rule and the direction (before, not after); it is not vitamin-specific.
Tested prescription drugs, not vitamins; single doses in healthy volunteers.
Source 3: federal nutrient fact sheet
ods.od.nih.gov · Source check Sep 22, 2026
Population: General population; no colesevelam co-use data
Vitamin D2 and D3 are inert until converted to 25-hydroxyvitamin D, the status marker; deficiency causes osteomalacia 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; bile acid sequestrants are not mentioned.
How this applies: Defines the supplement forms, the status test, the upper limit and deficiency signs.
General nutrient guidance; no colesevelam 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 colesevelam and Vitamin D article from inspected current labeling and original sources, with uncertainty stated. |
Article revision: 0a6e2cefcb4643c9
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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