Antibiotics Interactions

Calcium in dairy products binds to tetracycline and fluoroquinolone antibiotics in the gut, forming complexes that are poorly absorbed and can substantially reduce the antibiotic's effectiveness.

Calcium can bind to certain antibiotics (tetracyclines and fluoroquinolones) in the gut and reduce how much of the drug is absorbed.

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.

Taken at the same moment, an antibiotic can kill bacterial probiotic organisms before they reach the gut, lowering the probiotic's benefit. Spacing the doses apart fixes it.

Antibiotics can kill the live bacteria and yeast in kefir if both are taken at the same time, and dairy calcium can bind certain antibiotics (tetracyclines, fluoroquinolones) and reduce their absorption. Spacing kefir a couple of hours away from each dose addresses both concerns. Note that the broader claim that kefir prevents antibiotic-associated diarrhea is not well supported: the one randomized trial of kefir itself found no benefit.