Maintenance of iron-related blood markers requires a positive iron balance — iron absorption through dietary sources needs to be greater than the amount of iron we lose. It is normal to lose a small amount of iron per day,[1] though a daily blood loss greater than 5-10 milliliters per day exceeds the amount of iron that can be absorbed from the average diet.[2] The following are potential causes of iron deficiency anemia, since they can affect either iron loss or iron absorption. These are listed in approximate order of decreasing prevalence:
Certain medications may reduce iron absorption, such as antacids, H2 blockers, and proton pump inhibitors, since these reduce acidity in the stomach.[2]
The presence of iron deficiency anemia in people without a menstrual cycle, especially in those over 50 years old, can be concerning since there may be blood loss occurring from a serious issue like gastric or colorectal cancer.[2][3]