This iron deficiency calculator solves the problem faced by many internal medicine doctors who are dealing with a prevalent pathology - iron deficiency anemia. Using the Ganzoni equation, it determines precisely how much iron-containing medicine they need to give parenteral (as iron infusions) to replenish the deficit. Don't forget to take a look at the iron-rich foods table to make sure you take care of your iron intake. And if you've been feeling a little bit under the weather recently, browse the anemia symptoms list to check if you could be suffer from this condition.

We try our best here at Omni to make our calculators as precise and reliable as possible. However, this tool can never replace a professional doctor's assessment. Before administering any drug, fluid, or treatment to your patient, make sure you know the correct dose and method.

How to use iron deficiency calculator

You can use the calculator when you need to find out how much iron must be given parenterally (non-orally) to a patient to supplement their iron stores, so that they are at a healthy level of hemoglobin.

  1. Input the patient's weight into the calculator. Remember, if they're overweight, you should use their ideal body weight, and if they're underweight (when their BMI is below 18.5) - use their actual body weight.
  2. Input the actual hemoglobin level. You can use whatever units are most convenient for you - this calculator will deal with all of them.
  3. Fill in the target hemoglobin level. The normal hemoglobin level is 12-15.5 mg/dL for women and 13.5-17.5mg/dL for men. You will want to tailor the desired hemoglobin level to the particular patient's needs, e.g., set it higher for pregnant women.
  4. You don't have to worry about the iron stores. The calculator will find it automatically, as it is based on the patient's weight.
  5. The calculator will then do its magic using the Ganzoni equation - and then your result is ready!

Remember that the result given by this calculator only refers to parenteral-administered iron. Oral supplements and iron-rich foods are absorbed differently; therefore, the doses will vary.

What is iron deficiency anemia?

Anemia, from the Ancient Greek for literally 'lack of blood', is medically defined as diminished levels (at least two standard deviations) of hemoglobin, hematocrit, and red blood cell count. Checking these parameters, we can also asses a parameter known as hemoconcentration - you can find more about it in our hematocrit/hemoglobin ratio calculator.

Iron deficiency anemia means a decreased or insufficient production of the red blood cells, due to low iron stores in the body. It is the most common nutritional disorder globally - in the USA, it affects 2% of men and 10-20% of women (depending on ethnicity). Iron deficiency is responsible for 25% cases of any anemia.

Having a low red blood cell count results in inadequate levels of the oxygen-carrying protein that is found inside those cells - hemoglobin. Without this protein, your tissues and organs cannot get the right amount of oxygen, producing anemia symptoms.

The causes of this type of anemia are:

  • insufficient dietary iron intake - especially in states of increased demand, like pregnancy or puberty;
  • heavy menstruations or abnormal postmenopausal bleedings in women;
  • gastrointestinal bleedings - potentially due to gastric ulcers or colorectal cancer;
  • impaired absorption - e.g., after bariatric surgery or after a gastrectomy.

Anemia symptoms

As mentioned above, the symptoms of iron deficiency anemia are caused by insufficient oxygen supply. The anemia symptoms are common for all types of anemia, and include:

  • shortness of breath;
  • weakness, fatigue;
  • fast heart rate - over 100 beats per minute, called professionally tachycardia;
  • headaches and dizziness;
  • chest pains;
  • paleness;
  • brittle, thin hair and nails;
  • cold hands and feet;
  • soreness of your tongue, cheilosis.

If you experience any of these symptoms, you may have iron deficiency anemia or another type of anemia. You should make an appointment with your physician, who will perform an examination and order some laboratory tests to confirm the diagnosis.

Iron deficiency anemia treatment - oral supplements or iron infusion?

The first step in treating any anemia should be identifying the underlying cause. This may require specialist examinations, such as a gastroscopy or visiting a gynecologist.

No matter the cause, the iron deficiency must be replenished. If the deficit is not that big, oral iron supplementation is the go to therapy. It is usually continued for at least three months after the deficit is corrected. This treatment is likely to be uncomfortable, as it causes gastrointestinal problems, including nausea or constipation. Therefore not everyone can tolerate it.

Iron infusion treatment may be used when there's a need to quickly replenish the deficiency, when the patient doesn't tolerate oral iron supplements or when their ability to absorb oral iron is insufficient (e.g., patients after a gastrectomy or bariatric surgery). Another such situation is a patient with inflammatory bowel disease with worsening symptoms.

The iron infusion is usually given 2-3 times a week - but not every day! A standard dose is usually 100-200mg of iron.

The drug dosage - Ganzoni equation

In our iron deficiency calculator, we use the Ganzoni equation, which is a widely-known formula to assess the patient's deficiency.

iron deficit [mg] = body weight [kg] * (target Hb [g/dL] - actual Hb [g/dL]) * 2.4 + iron stores [mg]

Hb = hemoglobin

The factor 2.4 is equal to 0.0034 * 0.07 * 1000, numbers which come from a number of assumptions:

  • Blood volume is roughly 7% of the body weight (or you can count it more accurately with our blood volume calculator)
  • The iron content of hemoglobin is 0.34%
  • 1000 converts g (grams) to mg (miligrams)

It is worth noting that the result from the Ganzoni formula is the cumulative iron dose that a patient needs to take in order to replete the iron stores in their body. The next step would be dividing this amount into individual doses per iron infusion.

How to support anemia treatment - iron-rich foods

Taking the right supplements at the correct dose (either an oral supplement or ab iron infusions) is the base of any anemia treatment, but you can support it a lot by just adjusting your diet a little bit. First - make sure you are eating the right amount of macronutrients to make sure your body has the energy to produce blood cells. Second - we listed some iron-rich foods here. Putting more of these into your diet will definitely help you recover and prevent anemia in the future.

fish & meat shellfish
liver (and other organ meats)
vegetables spinach
legumes (beans, lentils, soy, peas, chickpeas)
grains quinoa
brown meat
whole wheat
others dark chocolate
pumpkin seeds, and other seeds as well
dried fruit

You can easily improve iron absorption by eating it together with vitamin-C rich foods, like citrus fruit, berries, tomatoes, or parsley.

Aleksandra Zając, MD
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