Actually, do not take an iron supplement or eat an iron-rich food within two hours of drinking coffee or tea. The reason is that polyphenols in coffee, black tea and green tea bind to iron, which keeps your body from absorbing it. Even decaf coffee and tea will keep the iron from being absorbed.
So if you are taking an iron supplement, and still feeling tired, it could be that you are drinking coffee or tea too soon after or before taking your iron.
If the wait seems too long for you, studies show that taking a 10mg. lycopene supplement with your tea or coffee will keep the polyphenols from binding to the iron, so your body can still absorb it.
But as always, please check with your own doctor before changing or taking any vitamins!