You shouldn't take iron supplements while consuming coffee because coffee inhibits iron absorption from both supplements and food. If you are taking iron supplements and eating high-iron foods, you should consume them at least one hour before and more than one hour after consuming coffee and other iron absorption inhibitors.
DRI: Recommended Dietary Allowance for Iron
Men age 19 and older require 8 milligrams of iron per day. Woman age 19 to 50 have a recommended intake of 18 milligrams per day; age 51 and older need 8 milligrams per day. Pregnant women of all ages have recommended iron intakes of 27 milligrams daily. For male and female adolescents age 9 to 13 years, recommended amounts of iron are 8 milligrams daily.
Enhance Iron Absorption
Vitamin C enhances iron absorption, particularly from nonheme iron. Eat citrus fruits, peppers, spinach and other vitamin C-containing foods when taking iron pills to enhance absorption. Immediately before and after taking iron pills, avoid tannins -- found in tea and coffee; high-fiber foods; soy protein; and calcium supplements.