What causes a low red blood cell count?

The most common causes of low red blood cell count are: 

1. Iron deficiency: Excessive loss of blood, insufficient iron intake via nutrition, and inefficient iron absorption from food are the main causes of iron deficiency that leads to anemia, which is a symptom of low red blood cell count. Anemia may also be caused during pregnancy due to the fetus’ higher demand for iron supply. 
2. Certain medical treatments: Certain cancer treatments, such as radiation therapy or chemotherapy, use radiation and strong chemicals, which destroy large amounts of red blood cells during every session, leading to diminished red blood cell count. 
3. Hemolysis: Autoimmune reactions to an infection, blood transfusion, or genetic disease such as sickle cell anemia, can lead to hemolysis, a condition in which the red blood cells break down or get destroyed. 
4. Excessive menstruation: Women who experience very heavy menstrual blood flow regularly are more likely to have low red blood cell count, especially if they do not take steps to compensate for the loss adequately through their diet.