What is. A good diet pill if I lack iron?

Ferrous sulfate. Over the counter pills containing ferrous sulfate are inexpensive and effective for iron deficiency. It would be a good idea to have blood tests to see if you have iron deficiency and not some other disorder.
Iron and Diet. Dear marina, before you try taking any "diet" pill, find out why you lack iron? Please get a complete history and physical from a certified physician. Iron deficiency can happen from many causes, some of them are very serious. Please do not diet until your iron deficiency is diagnosed and treated. Good luck.