Why ferrous sulfate reccomended for anemia?

Iron: Most common cause of anemia is iron deficiency, so ferrous sulfate gives you the iron you are missing.

Make new blood cells: Iron is a very important mineral the body uses to make new red blood cells. If you are anemic, it means you are short of red blood cells. You either lost them due to bleeding, you are destroying them too fast (like sickle cell), or you can't make new ones fast enough to keep up with your needs. Whatever the reason, you need the iron (ferrous) to make new ones.