Red blood cells (erythrocytes) are the carriers of gas in the blood. Oxygen and carbon dioxide to a lesser extent are transported by attaching to these cells. The red blood cell’s main oxygen carrying structure is hemoglobin which is made up of iron among other components. Anemia is a condition where the number of red blood cells or hemoglobin is lower than normal. In iron-deficiency anemia, this is due to a deficiency of hemoglobin associated with low iron availability. The low oxygen supply also leads to less red blood cells being produced. Ultimately this decreases the oxygen-carrying capacity of the blood and leads to a host of associated signs and symptoms.

Many young women, prior to their first pregnancy, suffer with severe constipation and anemia, which are often seen as unrelated symptoms. The anemia or low blood iron stems from the loss of blood due to menses while constipation is a gastrointestinal (gut) disorder resulting in difficulty in passing out feces (stool). However evidence suggests that both anemia and constipation may be linked to a common hormonal cause that plagues many menstruating women.