Stage 1 of IDA is a progressive decrease of storage iron. During this phase, red blood cell production and development continue without replacing storage iron. Symptoms are minimal, if present at all, and hematology findings will be within reference ranges. Serum ferritin levels, however, will fall below reference ranges.
A depletion of all storage iron represents Stage 2, and gradually hemoglobin production decreases. Red blood cell indices remain within reference ranges. Later in this stage, symptoms will start to appear, including muscle weakness.
Stage 3 represents true anemia with all the related signs and symptoms of iron deficiency anemia. Red blood cells first become microcytic, then hypochromic, as their ability to produce hemoglobin decreases.
