Pregnancy Iron Deficiency Calculator

Estimates the prenatal iron deficit based on patient weight, haemoglobin and iron stores.

In the text below the form there is more information about the formula used and about prenatal iron deficiency.

The iron deficiency calculator uses pregnancy weight, target and actual haemoglobin values and iron stores to determine the iron deficit.

The patient weight is used to compute the prenatal iron deficit per kilogram. This determination helps guide iron supplementation.

The formula used is that of Ganzoni:

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

Target Hemoglobin:*
Actual Hemoglobin:*
Iron Stores in mg:*
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Steps on how to print your input & results:

1. Fill in the calculator/tool with your values and/or your answer choices and press Calculate.

2. Then you can click on the Print button to open a PDF in a separate window with the inputs and results. You can further save the PDF or print it.

Please note that once you have closed the PDF you need to click on the Calculate button before you try opening it again, otherwise the input and/or results may not appear in the pdf.


Variables and Ganzoni formula

Pregnancy iron deficit is determined based on pregnancy weight, actual and target haemoglobin levels and the size of iron stores in miligrams.

There is a variation as to what measurement units can be used:

■ Weight can be input in lbs or kg;

■ Hemoglobin can be input in g/dL, g/L or mmol/L.

For the size of the iron store, the recommended input is of at least 500 mg for all patients weighing more than 35 kg.

The Ganzoni formula determines the iron deficit:

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

Actual haemoglobin levels may be affected by state of dehydration or hyperhydration. The threshold for anemia diagnosis in pregnancy differs across the three trimesters:

■ Less than 11 g/dL Hb during first trimester;

■ Less than 10.5 g/dL Hb during second trimester;

■ Less than 10 g/dL Hb during third trimester.


Iron deficiency in pregnancy

In pregnancy, the most commonly met deficiency is that of iron. If left untreated this leads to adverse outcomes and RBC transfusion.

Iron deficiency is usually diagnosed during one of the full blood count tests that pregnant women undergo (at least 2, with the first at 28 weeks of pregnancy).

During pregnancy, the volume of blood in the body increases by almost 50% which leads to a decrease in hemoglobin concentration. When iron stores are not increased from an external source, they cannot support the new requirement of hemoglobin for the newly forming red blood cells.

To avoid this type of deficiency, pregnant women are to receive nutritional advice into how they can maximize iron intake and iron supplements are prescribed routinely in the prenatal vitamins pack.

In case iron deficit is confirmed, oral therapy is initiated, with 100 to 200 mg of daily elemental iron.

If oral iron intolerance takes place or the repletion is not in schedule, parenteral iron may be considered, but only from the second trimester.



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

2. Bayoumeu F, Subiran-Buisset C, Baka NE, Legagneur H, Monnier-Barbarino P, Laxenaire MC. Iron therapy in iron deficiency anemia in pregnancy: intravenous route versus oral route. Am J Obstet Gynecol. 2002; 186(3):518-22.

3. Shafi D, Purandare SV, Sathe AV. Iron Deficiency Anemia in Pregnancy: Intravenous Versus Oral Route. J Obstet Gynaecol India. 2012; 62(3): 317–321.

Specialty: Obstetrics Gynecology

System: Reproductive

Objective: Determination

Type: Calculator

No. Of Variables: 4

Article By: Denise Nedea

Published On: May 26, 2017

Last Checked: May 26, 2017

Next Review: May 26, 2023