Laboratory tests showed severe _____, an abnormally low red blood cell count or hemoglobin level.

Anemia is a condition where the blood lacks enough healthy red blood cells to carry adequate oxygen to tissues. It can be caused by decreased production of red blood cells, increased destruction of red blood cells, or blood loss. Common symptoms include fatigue, weakness, shortness of breath, and pale skin.

Anemia Types and Characteristics:
- Iron deficiency anemia: Most common type, caused by insufficient iron
- Aplastic anemia: Bone marrow fails to produce blood cells
- Sickle cell anemia: Inherited condition affecting hemoglobin
- Vitamin B12 deficiency anemia: Also called pernicious anemia
- Hemolytic anemia: Premature destruction of red blood cells

Key Terms:
- Hemoglobin: Protein carrying oxygen in red blood cells
- Hematocrit: Percentage of blood volume occupied by RBCs
- Erythropoiesis: Process of red blood cell production
- Microcytic: Smaller than normal red blood cells
- Macrocytic: Larger than normal red blood cells

Diagnostic Tests:
- Complete Blood Count (CBC)
- Serum ferritin test
- Peripheral blood smear
- Reticulocyte count
- Iron studies

Treatment Approaches:
- Iron supplementation
- Vitamin B12 injections
- Folic acid supplements
- Blood transfusions
- Bone marrow transplantation

Normal Values:
- Hemoglobin: 13.5-17.5 g/dL (male), 12.0-15.5 g/dL (female)
- Hematocrit: 41-50% (male), 36-44% (female)
- RBC count: 4.5-5.9 million/mcL (male), 4.1-5.1 million/mcL (female)