Iron is one supplement that people need medical supervision to use safely. Too much iron will be stored in the body in a toxic way. I don't recommend iron unless people have evidence of anemia and a doctor has told them how much to take and for how long. Sometimes it is only for a few months.

Poor acid quality in the stomach, from drugs like Zantac or Prilosec will reduce iron absorption, as acid is a cofactor for proper iron absorption from food.

Anemia can be common in women who have heavy periods. This happens typically just before menopause starts for some of them.