Can I take Keflex (Cephalexin) if I'm on an iron supplement?

Can You Take Keflex with Iron Supplements?

Yes, you can safely take Keflex (cephalexin) with iron supplements without any clinically significant interaction or need for dose separation.

Key Points About This Combination

• No documented interaction exists between cephalexin (Keflex) and iron supplements in the medical literature 1
• Cephalexin is a first-generation cephalosporin antibiotic that does not form chelation complexes with iron, unlike certain other antibiotics 1, 2
• You can take both medications at the same time without concern for reduced effectiveness of either drug

Important Context: Which Antibiotics DO Interact with Iron

While Keflex is safe with iron, you should be aware that other antibiotics require dose separation from iron supplements:

Fluoroquinolones (Require Separation)

• Ciprofloxacin absorption is reduced by approximately 50% when taken with standard iron supplements 3, 4
• Take ciprofloxacin at least 1-2 hours before or 4 hours after iron-containing preparations 3
• This interaction occurs because iron forms chelation complexes with fluoroquinolones, preventing absorption 1, 4

Other Cephalosporins (Require Separation)

• Cefdinir (a different cephalosporin) shows marked impairment when taken with iron, with area under the curve reduced by over 90% 2
• Even when iron is given 3 hours after cefdinir, absorption is still significantly reduced 2
• However, cephalexin (Keflex) does not share this interaction 1

Additional Antibiotics Affected by Iron

• Tetracyclines (tetracycline, doxycycline, methacycline, oxytetracycline) form stable complexes with iron and should be separated 1

Practical Recommendations for Your Situation

• Take your Keflex and iron supplement together if convenient, or at separate times—either approach is acceptable 1
• Continue your iron supplementation as prescribed without interruption during your Keflex course
• No dose adjustments are needed for either medication

Common Pitfall to Avoid

• Do not confuse cephalexin (Keflex) with cefdinir—these are different cephalosporin antibiotics with different interaction profiles 2
• If you are prescribed a fluoroquinolone antibiotic (like ciprofloxacin, levofloxacin) in the future, remember that those do require separation from iron 3

Monitoring Your Iron Therapy

• Iron supplements commonly cause dark or black stools, which is a benign side effect 5
• Common gastrointestinal side effects include constipation (12%), diarrhea (8%), and nausea (11%) 5
• If you experience intolerable side effects from iron, consider taking it with food (though this reduces absorption) or switching to alternate-day dosing 5