Which nutrient deficiency causes iron deficiency anemia?

• A. Vitamin B12
• B. Folate
• C. Iron
• D. Calcium

Answer: (C)

This question hinges on how specific nutrient deficiencies affect red blood cell production. Iron is essential for forming hemoglobin, the protein that carries oxygen in red blood cells. When iron stores are insufficient, the body can’t synthesize enough hemoglobin, so red blood cells become smaller (microcytic) and paler (hypochromic). This pattern defines iron deficiency anemia. Everyday clues like fatigue, pallor, and sometimes pica, plus lab cues such as low ferritin and low serum iron with high TIBC, fit this deficiency.

The other nutrients don’t cause this specific type of anemia. Vitamin B12 deficiency leads to macrocytic anemia with larger red blood cells and possible neuropathy, not the small, pale cells seen in iron deficiency. Folate deficiency produces a similar macrocytic pattern. Calcium has no direct role in hemoglobin synthesis or red blood cell size. Therefore, iron itself is the deficiency that causes iron deficiency anemia.