Taking an iron supplement can reverse a deficiency, but only if your body is absorbing all the iron. That's why it's key to know the best time to take iron supplements to get the most benefits. Once they have confirmed that an iron supplement is appropriate for you, here’s what you need to know about iron supplements, including the best time of day to take yours and what medications to avoid while taking iron. In addition to the best time of day, Castelli said the frequency at which you take your iron supplements can also play a role in absorption. “It is highly recommended that you take your iron supplement with your vitamin C supplement,” she said.