Estimate total iron deficit using the Ganzoni formula.
Total iron deficit (mg) = Body weight (kg) × 0.24 × (Target Hb − Actual Hb) × 10 + Iron stores. The factor 0.24 = 0.0034 (iron content of Hb) × 0.07 (blood volume as fraction of body weight) × 1000. Default iron stores are 500 mg for adults >35 kg. This is the standard formula for calculating IV iron replacement.