The short answer
Oral iron can substantially reduce the amount of ciprofloxacin absorbed. The current tablet label directs ciprofloxacin at least 2 hours before or 6 hours after an iron-containing product. Ferrous sulfate and ferrous gluconate have both been studied, but the reduction is not identical for every formulation.
What this answer covers
Oral ciprofloxacin tablets and oral iron preparations. Intravenous iron and injected ciprofloxacin are not assessed by these gut-absorption studies.
- Supplement or preparation
- Iron
- Medication ingredient
- ciprofloxacin
How much can absorption change?
In one 12-person study, ciprofloxacin exposure fell substantially when a 500 mg antibiotic dose was taken with ferrous sulfate after a week of iron dosing. A separate eight-person study found reduced exposure with ferrous sulfate and ferrous gluconate. These studies establish a clinically relevant concern about low antibiotic concentrations, although they did not directly count treatment failures in infected patients.
Does changing the iron salt solve the problem?
The second study tested two iron salts, and both reduced ciprofloxacin exposure. Their effects differed, so one number cannot describe every iron supplement. The data do not establish that a newer iron complex, liquid product, or a lower strength can be taken simultaneously without concern. The current label therefore gives an instruction for iron-containing products rather than only one brand.
Which medicine should be taken first?
Use a directional schedule: ciprofloxacin first means leaving at least 2 hours before the iron product; iron first means waiting at least 6 hours before ciprofloxacin. An instruction saying only “separate by two hours” leaves out this distinction. Check multivitamins and prenatal products too, because an iron-containing combination can create the same scheduling problem.
What if I need iron every day?
The interaction does not mean you must permanently stop treatment for iron deficiency. Your pharmacist can fit your prescribed iron and antibiotic doses into a practical plan, accounting for other medicines and mineral products. After an accidental overlap, ask for individual advice rather than increasing the antibiotic dose. These studies cannot calculate the absorbed amount for a particular person or product.
Evidence and practical considerations
Absorption & effectiveness
Oral iron can substantially reduce the amount of ciprofloxacin absorbed. The current tablet label directs ciprofloxacin at least 2 hours before or 6 hours after an iron-containing product. Ferrous sulfate and ferrous gluconate have both been studied, but the reduction is not identical for every formulation.
- Exact scope
- oral iron-containing preparations, with direct ferrous sulfate and ferrous gluconate evidence with oral ciprofloxacin hydrochloride tablets expressed as ciprofloxacin
- Medication form and route
- oral
- Timing or duration
- An interaction was observed when oral doses overlapped, including after seven days of iron use.
What remains uncertain
- Small human pharmacokinetic trials; no measured clinical failure rate. Evidence is direct for tested oral salts and cannot be transferred to intravenous administration.
Factors that may matter: exact formulation and mineral content; order and timing of doses; other minerals in the same product.
Read the supporting source summaries
Source 1: regulatory product label
dailymed.nlm.nih.gov · Source check Sep 10, 2026
Population: Patients prescribed oral immediate-release ciprofloxacin tablets.
The label identifies impaired absorption and directs ciprofloxacin at least 2 hours before or 6 hours after the listed cation products.
How this applies: The source explicitly describes ciprofloxacin hydrochloride tablets in ciprofloxacin-equivalent strengths, supporting a bounded oral tablet application to the parent ingredient RxCUI 2551. It does not merge parent and salt identities. Exact article counterparty: oral iron-containing preparations, with direct ferrous sulfate and ferrous gluconate evidence.
Product labeling does not provide a separate effect size for every supplement salt, amount, or formulation. These timing instructions are for the oral product.
Source 2: human pharmacokinetic study
pubmed.ncbi.nlm.nih.gov · Source check Sep 10, 2026
Population: Twelve healthy adult male volunteers in a four-period crossover study.
Ciprofloxacin AUC was 5.4 with ferrous sulfate and 11.3 with the multivitamin versus 14.5 and 15.7 microgram-hours/mL in the two control periods.
How this applies: Direct ferrous sulfate and multivitamin-with-zinc evidence. Indirect for zinc alone or other multivitamin compositions.
The multivitamin arm cannot identify the responsible component, and the trial measured exposure rather than clinical treatment failure. Original author abstract inspected; full study text was not assessed.
Source 3: human pharmacokinetic study
pubmed.ncbi.nlm.nih.gov · Source check Sep 10, 2026
Population: Eight healthy subjects in a clinical crossover comparison.
AUC declined from 12.3 mg-hours/L alone to 6.7 with ferrous sulfate, 4.1 with ferrous gluconate, and 5.4 with the combined mineral tablet.
How this applies: Direct evidence for the tested iron salts and particular combined mineral tablet; not a quantified zinc-only or all-multivitamin effect.
Small pharmacokinetic study. Individual mineral contributions in the combined product are inseparable. Original author abstract inspected; full study text was not assessed.
Research assessment: · Open full citations ↗
Review and change history
- Publication status
- Published research summary
- Clinical review
- Not yet recorded
| Date | Update |
|---|---|
| Article prepared | |
| Original sources checked, exact preparations documented, and the imported statements reconciled in a complete private article draft. | |
| Research summary published |
Article revision: ad4d4fc5b8791ac6
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.
Taking other supplements or medications?
Use the checker to explore your other combinations. Ask a pharmacist to review the exact products, amounts and medical conditions in your complete list.
Open the interaction checkerInformation, not medical advice. Do not change prescribed treatment based on this guide.