Iron supplements are best absorbed on an empty stomach when taken with water or orange juice, as vitamin C is thought to increase iron absorption, according to Tamburello.
“However, iron supplements tend to cause GI upset and constipation, especially when taken on an empty stomach,” she says. “This is why it’s best for some to take their iron supplement after a meal (although it does decrease absorption).”
It’s also typically best to avoid taking an iron supplement with foods, as high-polyphenol and high-phytate foods including tea, coffee, wine, certain fruits, vegetables, legumes, and cereals can interfere with iron absorption, Tamburello says. Note that calcium supplements and antacids can also decrease the absorption of iron supplements.
