Lower than normal numbers of RBCs may occur with bleeding, bone marrow failure, malnutrition, kidney disease, overhydration, or pregnancy. Several drugs affect the level of RBCs and may make it higher or lower than normal.

What happens when red blood cells decrease?

A low red blood count, or anemia, can cause feelings of fatigue and weakness. When a person has a lower red blood count than is normal, their body has to work harder to get enough oxygen to the cells. A low red blood cell (RBC) count can cause a variety of symptoms and health complications.

Why do blood cells decrease?

Possible Causes

A low white blood cell count is associated with certain conditions, including: Cancer (caused by chemotherapy treatments) Bone marrow disorders or damage. Autoimmune disorders (problems with the immune system in which the body attacks itself), such as lupus.