- Iron deficiency is the leading cause of anemia worldwide due to its essential role in hemoglobin synthesis.
- Insufficient iron intake, absorption, or increased loss leads to reduced hemoglobin production, causing microcytic, hypochromic anemia.
- This is especially prevalent in populations with poor nutrition, chronic blood loss, or increased demand (e.g., pregnancy).
- Iron deficiency anemia results in symptoms related to inadequate oxygen delivery to tissues.
- Other causes like vitamin B12 deficiency lead to macrocytic anemia, while chronic kidney disease causes anemia mainly by reduced erythropoietin, and thalassemia is a genetic cause of defective globin synthesis but less common globally than iron deficiency.

Reference: Davidson’s Principles and Practice of Medicine, 23rd Edition, Chapter: Disorders of Red Blood Cells and Bleeding, Page 395.