Iron Deficit Calculator (Ganzoni)

How it is calculated

Enter body weight in kilograms, the patient's current haemoglobin and the target haemoglobin, both in g/dL. The tool applies the Ganzoni formula: deficit (mg) = weight × (target Hb − actual Hb) × 2.4 + 500. The product of the first three terms is the iron needed to rebuild haemoglobin, and the added 500 mg stands for iron stores.

The stores amount is always 500 mg in this tool, whatever the weight. Some references use a different stores figure for children or low body weight, so for those patients the clinician's own value should replace it. The target must be higher than the actual value, and weight must be above zero, or there is no result. The answer is in mg with two decimals. It is a calculation aid only and not a dosing instruction.

Common mistakes

• Entering haemoglobin in g/L (for example 90 instead of 9). The factor 2.4 is built for g/dL, so g/L inputs overstate the deficit about tenfold.
• Entering weight in pounds. The formula needs kilograms.
• Swapping the target and actual values. The target must be higher than the actual one; if it is not, the tool shows nothing.
• Assuming the 500 mg stores term adjusts for children or small adults. Here it is constant, so the result for a light patient may need a clinician's adjustment.
• Reading the result as a prescription. Dosing, product choice and the number of infusions depend on the clinician and on the drug used.