Which laboratory value typically decreases in iron deficiency anemia?

In iron deficiency anemia, the laboratory value that typically decreases is ferritin. Ferritin is a protein that stores iron in the body, and its levels are reflective of the body's iron stores. When there is a deficiency of iron due to inadequate dietary intake, chronic blood loss, or other causes, the levels of ferritin will drop as the body can no longer maintain sufficient iron stores needed for the production of hemoglobin and red blood cells.

In this condition, hemoglobin may also be decreased, but ferritin is specifically linked to the iron stores and is the first laboratory value to show a significant decline in response to iron deficiency. White blood cell count and platelet count are not typically decreased in iron deficiency anemia; in fact, the platelet count can sometimes even be elevated. Thus, the decrease in ferritin is a clear indicator of iron deficiency and is a critical measure in diagnosing and assessing the severity of iron deficiency anemia.