tetracycline
6 interactions related to tetracycline
doxycycline + iron
Iron forms an insoluble chelate complex with doxycycline in the gut, sharply reducing absorption of the antibiotic. In controlled human studies, ferrous sulfate taken together with doxycycline cut serum antibiotic levels substantially, which can undermine treatment.
doxycycline + magnesium
Magnesium ions can bind doxycycline in the gastrointestinal tract, forming a poorly absorbed complex that reduces how much antibiotic reaches the bloodstream. Magnesium-containing supplements, antacids, and laxatives can meaningfully lower doxycycline absorption if taken at the same time.
doxycycline + calcium
Calcium binds doxycycline in the gut, forming a complex the body cannot fully absorb. Taking doxycycline together with calcium supplements, calcium-based antacids, or large dairy servings can lower how much antibiotic reaches the bloodstream, though doxycycline binds calcium less than older tetracyclines.
tetracycline + zinc
Zinc forms a chelate with tetracycline in the gastrointestinal tract, modestly reducing absorption of the antibiotic. The interaction also reduces zinc absorption. Doxycycline is much less affected.
tetracycline + calcium
Calcium binds to tetracycline in the gut, forming an insoluble chelate that the intestine cannot absorb. Dairy products, calcium supplements, and calcium-based antacids can sharply reduce how much tetracycline reaches your bloodstream, which can drop levels below what is needed to treat the infection.
yogurt + antibiotics
The calcium in yogurt can bind to certain antibiotics — specifically the tetracyclines and fluoroquinolones — in the gut and reduce how much of the drug is absorbed. This is the same chelation interaction seen with milk. Penicillins and macrolides are not meaningfully affected. The fix is timing: take these antibiotics with water and keep yogurt and other calcium-rich foods a couple of hours apart from the dose.