Ganzoni formula calculator: iron deficit in mg for anemia treatment
Calculate total iron deficit in mg using the Ganzoni formula (1970). Body weight, actual and target hemoglobin, iron stores – result guides IV or oral iron dosing.
Updated · Methodology
About this calculator
The Ganzoni formula is used in hematology and primary care to calculate daily and total iron doses in iron deficiency anemia. Equation: iron deficit (mg) = body weight × (target Hb – actual Hb) × 2.4 + depot iron. Target Hb is usually 130 g/L in women and 140 g/L in men. Depot is 500 mg for patients ≥ 35 kg and 15 mg/kg for patients < 35 kg. The calculator returns an absolute mg value useful for dosing ferric carboxymaltose, iron sucrose, iron(III) hydroxide polymaltose complex, or oral iron preparations. The formula applies only to confirmed iron deficiency anemia (low ferritin, low transferrin saturation); it does not apply to anemia of chronic disease. The ferric carboxymaltose label does not dose by the Ganzoni formula but by a table of haemoglobin and body weight. Below 10 g/dL that is 1500 mg for 35 to 70 kg and 2000 mg from 70 kg; at 10 to 14 g/dL, 1000 and 1500 mg; at 14 or above, 500 mg in both bands. Below 35 kg the requirement is calculated per kilogram. A single administration does not exceed 20 mg/kg by infusion or 15 mg/kg by injection, and never 1000 mg. The weekly cumulative dose is also capped at 1000 mg, so a 2000 mg requirement is split into two administrations at least seven days apart. Which weight to enter is the most frequent question: use actual body weight. Neither the formula nor the label directs you to substitute ideal weight, and the label table limits overestimation on its own, because it groups weight into bands and stops at 2000 mg. In pregnancy the label is restrictive. Data are scarce, treatment is limited to the second and third trimesters, and first-trimester deficiency is in many cases covered with oral iron. The fetus is monitored during intravenous administration: transient fetal bradycardia has been described alongside a maternal hypersensitivity reaction.
Source
Formula version: 1970-v1
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