- It is defined as a decrease in the total amount of red blood cells (RBCs) or hemoglobin in the blood
- Statistics: Normal values of HB in men -13 to 14 g/dL; Normal values of HB in women - 12 to 13 g/dL; 25% of global population is anemic; anemia is the most common disorder of the blood; the global mortality due to iron deficiency anemia in 2013 was 183,000
##The three main categories of causes of anemia are:
- Blood loss e.g. trauma, menorrhagia, fibroids, helminthiasis, over-sampling in anemia of prematurity and GIT bleeding
- Inadequate production of RBC e.g. iron deficiency, a lack of vitamin B12, thalassemia, and a number of neoplasms of the bone marrow.
- Excessive destruction of RBC e.g. sickle cell anemia, malaria and other infections, and some autoimmune diseases.
##Anemia is also classified based on the size of RBC and amount of hemoglobin in each cell as:
- Microcytic anemia (small size RBC) - due to hemoglobin synthesis insufficiency e.g. Iron deficiency anemia, Anemia of chronic disease, sideroblastic anemia, and alpha or beta-thalassemia
- Macrocytic anemia (large size RBC) - due to a deficiency of either vitamin B12, folic acid, or both
- Normocytic anemia (normal size RBC) – it occurs when the overall hemoglobin levels are decreased, but the red blood cell size remains normal e.g. acute blood loss, aplastic anemia, and hemolytic anemia