Given the correct sequence of Iron Deficiency Anaemia (IDA).
1. Fall in serum ferritin level.
2. Decrease in sustainable iron in bone marrow.
3. Fall in hemoglobin level.
4. Exhaustion of body iron reserves.

Iron deficiency anemia develops progressively in three distinct stages, moving from the depletion of bodily iron stores to impaired red blood cell production, and finally to clinically recognizable anemia.
Stage 1: Depletion of Iron Stores (Prelatent Stage)
Stage 2: Iron-Deficient Erythropoiesis (Latent Stage)
Stage 3: Frank Iron Deficiency Anemia