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 Captopril + Iron pair, each linking to PubMed by PMID where available. Full sourcing methodology at https://nutristackapp.com/methodology/interactions.

Supplement × Prescription·timing-sensitive·Moderate evidence

Captopril + Iron

Q: Can I take Captopril and Iron together?

Yes, if you separate them in time. Captopril and Iron have a documented timing-sensitive interaction. Oral iron salts can react with captopril, which contains a free sulfhydryl (thiol) group, forming a complex that reduces captopril absorption and may diminish its blood-pressure-lowering effect. Co-administration has been shown to lower captopril bioavailability.

Q: How does this affect a NutriStack Stack Score?

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

Timing Sensitive Moderate evidence

Oral iron salts can react with captopril, which contains a free sulfhydryl (thiol) group, forming a complex that reduces captopril absorption and may diminish its blood-pressure-lowering effect. Co-administration has been shown to lower captopril bioavailability.

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

Captopril and Iron

Pair type

Timing Sensitive

Evidence

Moderate

Source citations

Scope

Supplement × Prescription

Last verified

June 4, 2026

Timing SensitiveModerate evidence

What is happening. Oral iron salts can react with captopril, which contains a free sulfhydryl (thiol) group, forming a complex that reduces captopril absorption and may diminish its blood-pressure-lowering effect. Co-administration has been shown to lower captopril bioavailability.

Mechanism. Ferrous iron oxidizes and binds the reactive thiol group of captopril in the gastrointestinal tract, forming a poorly absorbed complex and reducing the amount of intact captopril available for absorption.

Recommendation. Separate doses. Take captopril at least 2 hours before or 2 hours after oral iron supplements to avoid reduced absorption of the ACE inhibitor.

Timing

Timing & separation.

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

Minimum separation

120

Stack Score

How it moves the number.

Effect on the composite score

If both Captopril and Iron 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

1Schaefer JP, et al. Effect of ferrous sulfate on the pharmacokinetics of captopril. British Journal of Clinical Pharmacology. 1998.Needs sourceNo link
2Campbell NR, Hasinoff BB. Iron supplements: a common cause of drug interactions. British Journal of Clinical Pharmacology. 1991.Needs sourceNo link

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