Zinc and medications: what to check

Zinc's two best-documented interactions are with antibiotics — quinolones and tetracyclines bind to zinc in the gut and absorb less well when taken at the same time — and with other minerals, where high-dose nonheme iron can reduce zinc absorption, and sustained high-dose zinc can reduce copper status. There's no established interaction between zinc and blood-thinning medication.

Quinolone and tetracycline antibiotics

A 2006 pharmacology review states plainly that all quinolone antibiotics form complexes with di- and trivalent cations, and that quinolone absorption can be dramatically reduced when taken along with mineral antacids, zinc or iron supplements. Tetracyclines behave similarly with minerals in general. The practical fix pharmacists give is separation in time — typically taking the antibiotic a couple of hours before or several hours after a zinc-containing supplement — but the exact spacing depends on the specific drug, so ask your doctor or pharmacist rather than guessing.

Iron

A 1981 controlled study found that nonheme iron (as ferrous sulfate) reduced zinc absorption when the two were given together as inorganic supplements, and that the effect got worse as the iron-to-zinc ratio rose — a 1:1 ratio slightly reduced zinc absorption, while 2:1 and 3:1 ratios reduced it substantially. Heme iron (the form in meat) didn't have this effect, and when zinc and iron were both consumed as part of a food (oysters plus added iron), the interaction disappeared too. In practice, this matters most for people taking a separate iron supplement alongside a separate zinc supplement, not for the iron and zinc that occur together in food.

Copper

Zinc and copper compete for absorption, and it runs in the opposite direction from the iron interaction above: it's high-dose, sustained zinc that reduces copper status, not the other way around. A 1984 controlled study found 50 mg/day of zinc for six weeks measurably reduced a marker of copper status in healthy men. This is why the adult upper intake level for zinc (40 mg/day) is set where it is — see zinc dosage for the full explanation.

Calcium

Calcium can also modestly interfere with zinc absorption when both are taken as concentrated supplements at the same time, though the effect is smaller and less consistently documented than the iron interaction above. Taking a large calcium supplement a few hours apart from a zinc supplement is a reasonable precaution if you take both.

Questions people ask

Does zinc interact with any medications?

The clearest documented interaction is with quinolone and tetracycline antibiotics, which bind to zinc and absorb less well when taken together — space them apart on your pharmacist's advice. There's no established interaction between zinc and most other medication classes, but tell your doctor about every supplement you take regardless.

Is zinc a blood thinner?

No. Zinc isn't classified as a blood thinner, and there's no established interaction between zinc supplements and anticoagulant medications in the research behind this page. Still, mention every supplement you take to your doctor if you're on a blood thinner.

Can I take zinc with iron?

You can, but taking large amounts of a separate iron supplement and a separate zinc supplement at the same time can reduce zinc absorption — a 1981 study found the effect grew with the iron-to-zinc ratio. Taking them a few hours apart avoids the issue; getting both from food doesn't trigger it.

Does zinc interact with copper?

Yes — sustained high-dose zinc reduces copper status, which is the main reason the adult upper intake level for zinc is capped at 40 mg/day. Many combination multivitamins include a small amount of copper specifically to offset this.

Related reading: how much zinc should you take a day, who should not take zinc, and zinc side effects.