Iron and Doxycycline Injection: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Doxycycline Injection
Iron
No brand names on record
How we grade severity & evidence
Severity levels
- Contraindicated: These should generally not be used together.
- Major: Potentially serious — often needs a change or close monitoring.
- Moderate: Can be significant — usually manageable with monitoring.
- Minor: Usually limited clinical impact.
Evidence grades
- Established: Well documented — supported by controlled studies or strong clinical data.
- Probable: Good supporting evidence, though not definitively proven.
- Suspected: Some evidence suggests this interaction, but it is not well established.
- Possible: Limited or conflicting evidence; the interaction may occur.
- Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.
Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.
What happens
Decreased tetracycline and iron effectiveness
Interaction Deep Dive
Separate the administration of iron products, such as ferric maltol, and doxycycline by at least 4 hours, as concomitant use may decrease the bioavailability of doxycycline and iron. Absorption of tetracyclines, including doxycycline, may be impaired by iron products. Monitor clinical response to doxycycline as appropriate1. The concurrent administration of ferrous salts (40 mg or more of iron) and tetracycline derivatives can lead to decreased levels of the tetracycline (50% to 90%) and decreased absorption of the ferrous salt (up to 50%) 6472. Staggered administration may not completely offset the decreased exposure of doxycycline 5.
Why it happens (mechanism)
Decreased tetracycline and iron absorption
Literature reports
2 reports — tap to read
a) Impaired gastrointestinal absorption of tetracycline by the concomitant administration of oral ferrous sulfate is well known. Ferrous sulfate has also been shown to interfere with the absorption of the tetracycline analogues oxytetracycline, methacycline, and doxycycline 23.
b) It has been demonstrated that a reduction in half-life of intravenous doxycycline from 16.6 hours to 11 hours occurs when given simultaneously with oral iron. The same study indicated that 200 mg of oral doxycycline given 3, 7, and 11 hours prior to 80 mg of elemental iron (ferrous sulfate) still resulted in a 20% to 45% reduction in serum doxycycline 4. Therefore, a 3-hour interval between dosing may not be adequate when doxycycline and iron are prescribed simultaneously 5.
Common questions
Can I take Iron and Doxycycline Injection together?
Decreased tetracycline and iron effectiveness Always confirm with your pharmacist or prescriber before making any change.
How serious is the Iron and Doxycycline Injection interaction?
It is rated moderate. Can be significant — usually manageable with monitoring.
How quickly could this interaction happen?
The documented onset is "delayed". Effects tend to build up gradually over days to weeks.
How strong is the evidence for this interaction?
The evidence is graded "probable". Good supporting evidence, though not definitively proven.
From our Q&A
Real reader questions about these medications, each personally answered by our pharmacist:
Questions for your pharmacist
- Does my dose of Iron or Doxycycline Injection need adjusting while I take them together?
- What symptoms should prompt me to call you or my prescriber right away?
- Does the timing of my doses matter for this combination?
- Is there anything you'd monitor while I'm on both?
References (7)
- Product Information: ACCRUFER(R) oral capsules, ferric maltol oral capsules. Shield Therapeutics Inc (per FDA), Austin, TX, 2022. DailyMed
- Neuvonen PJ, Gothoni G, Hackman R, et al: Interference of iron with the absorption of tetracycline in man. Br Med J 1970; 4:532-534.
- Neuvonen PJ: Interactions with the absorption of tetracyclines. Drugs 1976b; 11:45-54. PubMed
- Neuvonen PJ & Penttila O: Effect of oral ferrous sulphate on the half-life of doxycycline in man. Eur J Clin Pharmacol 1974; 7:361-363. DOI
- Cunha BA, Sibley CM, & Ristuccia AM: Doxycycline-review. Ther Drug Monit 1982; 4:115-135.
- Venho VM, Salonen RO, & Mattila MJ: Modification of the pharmacokinetics of doxycycline in man by ferrous sulfate or charcoal. Eur J Clin Pharmacol 1978; 14:277-280.
- Neuvonen PJ & Turakka H: Inhibitory effect of various iron salts on the absorption of tetracycline in man. Eur J Clin Pharmacol 1974; 7:357-360. PubMed
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