What kind of interaction is it?

Timing-sensitive: the two substances can be taken on the same day but should be separated by a minimum time window.

Is this interaction backed by published research?

Yes. NutriStack lists 2 citation rows for the Cholestyramine + Vitamin A pair, each linking to PubMed by PMID where available. Full sourcing methodology at https://nutristackapp.com/methodology/interactions.

Supplement × Prescription·timing-sensitive·Moderate evidence

Cholestyramine + Vitamin A

Q: Can I take Cholestyramine and Vitamin A together?

Yes, if you separate them in time. Cholestyramine and Vitamin A have a documented timing-sensitive interaction. Cholestyramine impairs absorption of fat-soluble vitamin A. Long-term therapy can lower serum vitamin A and beta-carotene levels, with potential for deficiency manifestations such as impaired dark adaptation in susceptible patients.

Q: How does this affect a NutriStack Stack Score?

-5 to your Stack Score per scored timing-sensitive row.

Timing Sensitive Moderate evidence

Cholestyramine impairs absorption of fat-soluble vitamin A. Long-term therapy can lower serum vitamin A and beta-carotene levels, with potential for deficiency manifestations such as impaired dark adaptation in susceptible patients.

Supplement × Prescription

Open the interaction checker → Read the methodology

From the database

What the row says.

Every entry follows the same shape: what is happening, the mechanism, and the recommendation.

Substances

Cholestyramine and Vitamin A

Pair type

Timing Sensitive

Evidence

Moderate

Source citations

Scope

Supplement × Prescription

Last verified

June 4, 2026

Timing SensitiveModerate evidence

What is happening. Cholestyramine impairs absorption of fat-soluble vitamin A. Long-term therapy can lower serum vitamin A and beta-carotene levels, with potential for deficiency manifestations such as impaired dark adaptation in susceptible patients.

Mechanism. Sequestration of bile acids reduces mixed-micelle formation required for absorption of fat-soluble vitamin A and carotenoids.

Recommendation. Separate administration, taking vitamin A at least 1 hour before or 4 to 6 hours after cholestyramine. Monitor vitamin A status in patients on prolonged high-dose therapy or with malabsorptive conditions and supplement if needed.

Timing

Timing & separation.

Space the doses apart by at least this window to avoid the conflict.

Minimum separation

240

Stack Score

How it moves the number.

Effect on the composite score

If both Cholestyramine and Vitamin A are in the same stack, this pair applies −5 to your Stack Score (per scored timing-sensitive row).

The full algorithm, the clamping rules, and four worked stacks are at /methodology/stack-score.

Sources

Sources, by evidence tier.

Every claim on this page is cited. PMIDs link straight to PubMed.

Reference material

1Questran (cholestyramine) US prescribing information. Drug interactions: fat-soluble vitamins (A, D, E, K).Needs sourceNo link
2West RJ, Lloyd JK. The effect of cholestyramine on intestinal absorption. Gut. 1975.Needs sourceNo link

Check your full routine

One pair was the worked example.

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Open the interaction checker → Browse the research index