Iron and your medicines: the same absorption trap as calcium

Iron — in food, and far more so in a supplement — binds the same drugs calcium does, and stops them being absorbed: levothyroxine, tetracyclines, fluoroquinolones. It also cuts both ways: those same medicines, and the coffee or tea people take them with, reduce how much iron you absorb from a meal. Every number below is one ordinary serving, from USDA FoodData Central.

By the pharmaranks editorial teamReviewed against USDA FoodData Central, the NIH Office of Dietary Supplements & FDA drug labels sourcesHow we research

The part people get wrong

Food iron is rarely the problem; an iron TABLET taken alongside your other pills is. Keep iron four hours away from levothyroxine, and — per the FDA label for ciprofloxacin — two hours before or six hours after a fluoroquinolone; about two hours either side for the tetracyclines. And if you are taking iron for anaemia, the tea or coffee you swallow it with is working against you — vitamin C helps, tannins hurt.

Iron in common foods — per serving, not per 100 g

Values from USDA FoodData Central for the serving shown. These are foods people actually eat: ranking the whole USDA database by density would put dried thyme and defatted soy flour at the top, which is accurate and no use to anyone.

Iron per serving in common foods (USDA FoodData Central)
Food	Serving	Iron (mg)
Beanswhite, mature seeds	1 cup (262 g)	7.8
Lentilsmature seeds, cooked	1 cup (198 g)	6.6
Spinachcooked, boiled	1 cup (180 g)	6.4
Chickpeasgarbanzo beans, cooked	1 cup (164 g)	4.7
Tofuraw, firm	0.5 cup (126 g)	3.4
Peasgreen, cooked	1 cup (160 g)	2.5
Beefground, 85% lean meat / 15% fat	3 oz (85 g)	2.3
Ricewhite, long-grain	1 cup (158 g)	1.9
Eggwhole, cooked	1 cup, chopped (136 g)	1.6
Potatoesbaked, flesh and skin	1 potato small (1-3/4" to 2-1/2" dia) (138 g)	1.5
Chickenbroilers or fryers, breast	0.5 breast, bone removed (145 g)	1.1
Broccolicooked, boiled	1 stalk, small (5" long) (140 g)	0.9

The medicines this affects

Drugs in our catalog from the classes involved — tetracycline-class drug, quinolone antimicrobial and thyroxine. Each page carries that drug’s own FDA label.

Check your own medicines against their FDA labels →

Frequently asked questions

Which foods are highest in iron?

Per serving, the highest on this list is beans — 7.8 mg in 1 cup (262 g), per USDA FoodData Central. These are common foods rather than the absolute maximum in the USDA database: ranking every food by iron density puts dried herbs and defatted soy flour at the top, which is true and useless to someone deciding what to have for dinner.

Do I need to avoid iron if I take these medicines?

Where do these numbers come from?

USDA FoodData Central (SR Legacy), for the household serving shown next to each food — not per 100 g. Per-100-g figures are what most "foods high in iron" lists use, and they are misleading: nobody eats 100 g of dried thyme.

Sources

Nutrient values are USDA reference data for the serving shown and vary with variety, growing conditions and cooking. This page is general information, not medical advice — never change your diet or your dose on the strength of a web page. Talk to whoever manages your treatment.