Since iron products interfere with absorption of oral tetracycline antibiotics, these two products should not be taken within 2 to 3 hours of each other.
Allergic hypersensitivity has occurred after administration of Vitamin B12 compounds. Iron salts are not well absorbed orally, and food may further impair their absorption. It may also decrease absorption of drugs like cefdinir, biphosphonates, entacapone, fluoroquinolones, levodopa, methyldopa, mycophenolate mofetil, and penicillamine. Iron salts may reduce the efficacy of levothyroxine.
Compounds containing calcium and magnesium, including antacids and mineral supplements, and bicarbonates, carbonates, oxalates or phosphates, may impair the absorption of iron by the formation of insoluble complexes. Zinc salts may also decrease the absorption of iron.
The response to iron may be delayed in patients receiving systemic chloramphenicol.
Ascorbic acid and citric acid may actually increase the absorption of iron.