Iron Deficiency Calculator

Variables and formula

There are four variables, all patient parameters, required in the iron deficiency calculator:

■ The patient’s weight is used in the Ganzoni equation and also when establishing the iron stores. Although the original formula requires the weight in kilograms, values input in lbs are transformed.

■ Patient’s measured hemoglobin can be input in g/dL or mmol/L.

■ A target haemoglobin value is also input so iron deficit can be determined according to a specified individual target. Normal haemoglobin values are gender specific: for males from 13.8 to 18.0 g/dL (138 to 180 g/L, or 8.56 to 11.17 mmol/L) and females from 12.1 to 15.1 g/dL (121 to 151 g/L, or 7.51 to 9.37 mmol/L).

■ Iron stores are input as default 500 mg on the assumption that the patient weight is greater or equal to 35 kg (77 lbs). In case a pediatric patient with a weight below 35 kg is assessed, iron stores are calculated as 15 mg iron for each kg.

The Ganzoni equation is:

Total iron deficit (mg) = Weight in kg x (Target Hb - Actual Hb in g/dL) x 2.4 + Iron stores           

In most cases, adult patients require a cumulative dose of elemental iron of at least 1 g. Most commonly, iron replenishment therapy is done intravenously:

■ As total dose (iron-dextran or iron – carboxymaltose);

■ As split dose (iron sucrose).

Iron deficiency anemia

Iron deficiency is common during childhood growth, prolonged periods of sickness, in convalescence or during pregnancy. There are physiological variation in iron reserves such as the decrease during menstruation period. On the other hand, slow decreases, such as that in chronic occult gastrointestinal bleeding are often difficult to diagnose.

Iron deficiency anemia is the type of anemia caused by iron depletion. IDA symptoms are often nonspecific and include tiredness, weakness, shortness of breath. Fulminant symptoms may include general paleness, confusion or episodes of passing out.

In less advanced cases of iron deficiency, increases in dietary intake of iron may be sufficient. Iron supplements, whether administered orally, intramuscular or intravenous, are used to replenish body stores and correct anemia.

Intravenous therapy is preferred for urgent intervention and when oral iron cannot be absorbed or the patient suffers from chronic renal impairment.

Original source

Ganzoni AM. Intravenous iron-dextran: therapeutic and experimental possibilities. Schweiz Med Wochenschr. 1970; 100(7):301-3.

Other references

1. Koch TA, Myers J, Goodnough LT. Intravenous Iron Therapy in Patients with Iron Deficiency Anemia: Dosing Considerations. Anemia. 2015: 763576.

2. Pasricha SR, Flecknoe-Brown SC, Allen KJ, Gibson PR, McMahon LP, Olynyk JK, Roger SD, Savoia HF, Tampi R, Thomson AR, Wood EM, Robinson KL. Diagnosis and management of iron deficiency anaemia: a clinical update. Med J Aust. 2010; 193(9):525-32.