Iron works both ways
Iron supplements can reduce the absorption of some medications, and some medications and foods change how well iron itself is absorbed. Most of these are timing issues solved by spacing doses.
Medicines iron can interfere with
- Levothyroxine (thyroid medication). Iron can bind levothyroxine; MedlinePlus advises taking iron and levothyroxine at least 4 hours apart [1] — see [supplements and thyroid medication](/learn/supplements-and-thyroid-medication).
- Certain antibiotics. Like other minerals, iron can reduce absorption of tetracyclines and fluoroquinolones; separate them by the hours described in [supplements and antibiotics](/learn/supplements-and-antibiotics).
- Some other drugs (for example, certain Parkinson's and osteoporosis medicines) can also bind iron — check with your pharmacist.
What affects iron's own absorption
- Vitamin C boosts non-heme iron absorption; calcium, tea, coffee, and acid reducers reduce it [2] — see [heme vs. non-heme iron](/learn/heme-vs-nonheme-iron-explained).
- Because stomach acid aids iron absorption, long-term acid reducers can lower how much iron you take up.
Practical guidance
- Separate iron from levothyroxine and affected antibiotics by about 4 hours (2 hours minimum for some).
- Pair iron with vitamin C and keep it away from calcium, tea, and coffee to aid absorption.
- Only take iron when there's a reason. Excess iron has its own risks, and it should be used when a clinician identifies a need (see [iron deficiency vs. overload](/learn/iron-deficiency-vs-overload)).
- Tell your provider and pharmacist about iron when starting any new medication.