Anemia due to iron deficiency is caused by the lack of nutrients essential for hematopoiesis. Iron, folate and vitamin B12 are all essential for healthy production of red blood cells. These components can become deficient due to issues with diet, or difficulties in absorption. This results in a reduction of the number of red cells circulating throughout the body.
A decrease in the hemoglobin content can lead to fatigue, paleness, and shortness-of-breath during physical exercise due to lowered oxygen carrying capacities within the bloodstream. In addition, a decreased erythrocyte counts can increase the risk of bleeding since there is less platelets present to aid in clotting when necessary. Untreated hypoxia can be caused by low levels of healthy red cells. Organs like the kidneys or heart could fail if they are not provided with enough oxygen.