Cefdinir and Iron: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Cefdinir
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 cefdinir efficacy; formation of reddish stools
Interaction Deep Dive
The coadministration of cefdinir and an iron supplement containing 60 mg of elemental iron as the ferrous sulfate salt or vitamins supplemented with 10 mg of elemental iron decreased the extent of cefdinir absorption by 80% and 31%, respectively. Therefore, cefdinir should be taken either two hours before or two hours after the administration of an iron supplement or a vitamin product containing iron. However, the coadministration of cefdinir oral suspension with iron-fortified infant formula has no significant effect on the pharmacokinetics of cefdinir1. Coadministration of cefdinir with iron-containing infant formulas may result in the development of reddish color stools. A case was reported of a 9-month-old infant who developed red stools after the concomitant use of cefdinir and iron-supplemented infant formulas. The postulated mechanism of action is formation of a nonabsorbable complex between ferric ions and either cefdinir or one of it metabolites 2. Use caution with the concurrent administration of cefdinir and iron-containing infant formulas. Monitor patient for appearance of reddish color stools.
Why it happens (mechanism)
Decreased cefdinir absorption; formation of a nonabsorbable complex between ferric ions and either cefdinir or one of it metabolites
Literature reports
1 report — tap to read
a) A case was reported of a 9-month-old infant who developed red stools after the concomitant use of cefdinir and iron-supplemented infant formulas. The patient had failure to thrive and otitis media and was prescribed cefdinir 62.5 mg orally twice daily (15.4 mg/kg/day) after experiencing an allergic reaction to amoxicillin-clavulanate. On the fifth day of therapy, the patient was brought to a clinic with the appearance of red stools that the mother described as the "consistency of tomato paste". The infant showed no signs of associated gastrointestinal symptoms (vomiting, abdominal pain, or diarrhea) and was clinically stable. The otitis media appeared resolved and cefdinir was discontinued. Laboratory values were a hemoglobin of 10.7 g/dL and hematocrit of 33.1 mg/dL. Stool cultures were negative along with a celiac disease panel. After discontinuation of the cefdinir, the infant's stools returned to normal within 48 hours. A follow-up complete gastrointestinal exam was negative. The clinical diagnosis was most likely C. difficile infection associated with antibiotic therapy. The infant was on an infant formula with iron along with breast milk. Three weeks later, the patient returned with recurrence of otitis media and cefdinir was restarted at 62.5 mg orally twice daily. Red stools were once again noted within 48 hours after cefdinir initiation. No other gastrointestinal symptoms were present and results of the stool guaiac test were negative. Within 24 hours after cefdinir discontinuation, the red stools were resolved. The recurrence of red stools with the second administration of cefdinir, the consistent timing of the events, and the rapid resolution of red stools after discontinuation of cefdinir support cefdinir in combination with iron-supplemented formulas as causative of this reaction. This adverse event was highly probable according to the Naranjo adverse drug reaction probability scale 2.
Common questions
Can I take Cefdinir and Iron together?
Decreased cefdinir efficacy; formation of reddish stools Always confirm with your pharmacist or prescriber before making any change.
How serious is the Cefdinir and Iron 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 Cefdinir or Iron 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 (2)
Keep reading about Cefdinir
Keep reading about Iron
These medications also interact with supplements
Prescription drugs aren't the whole picture — herbal and dietary supplements can interact with them too. From the evidence-graded Natural Medicines database:
major · moderate · minor — check everything you take with our drug–supplement interaction checker.
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