Iron Deficit Calculator
(For calculating intravenous iron requirements for all ages)
Notes regarding ferric carboxymaltose (Ferinject):
- Maximum 1000mg of i.v. iron per week (or 20mg/kg for those under 35kg)
- Do not dilute to less than 2mg/mL
- administer 100mg/min or over 15 minutes for 1000mg
- For children please use the 15mg/kg result, and only use if they are anaemic.
- POAC details https://www.poac.co.nz/ferinject/ Auckland Patients
- Special authority criteria
- Click for antenatal dosing schedule
- Check phosphate levels (and defer if <0.8) if:
- has had ≥ 2 iron infusions within the preceding 6 months.
- has received ≥ 1000 mg of ferrous carboxymaltose and is symptomatic with weakness, bone pain, or mental status change.
- is at risk of hypophosphataemia (BMI < 18, poor nutrition, chronic diarrhoea
Calculation Explanations
Ganzoni
Total Iron Deficit = Body Weight kg x (Target Hb – Actual Hb g/L) x 0.24 + Iron Reserve to Replenish Stores(mg) (1)
where
Target Hb = 140 for body weight ≥35 kg, 130 for body weight <35 kg, 110 if pregnant, 110-120 for CKD
Iron Reserve to Replenish Stores = 500mg for body weight ≥35 kg or 15 mg/kg body weight for body weight <35 kg. This part of the formula is hidden in the calculator. If you only want to correct the anaemia but not replenish stores then subtract 500 or 15mg/kg if body weight less than 35kg
Round down to nearest 100 mg if body weight ≤66 kg and round up to nearest 100 mg if body weight > 66 kg. Shown in parentheses in the calculator.
Use ideal weight in overweight patients, use actual weight in underweight patients.
This calculation method is based on first principles
UpToDate©
Total Iron Deficit = Body Weight kg x (Target Hb – Actual Hb g/L) x 0.2145 + Iron Reserve to Replenish Stores(mg) (2)
Similar to the Ganzoni method but uptodate uses a blood volume of 65mL/kg instead of 70mL/kg
Simplified
Please only use this alternative method with caution as it is based on a single trial of patients with inflammatory bowel disease. It tends to give quite different values to using the Ganzoni method.
MUST NOT be used in for patients under 35 kg in weight (3).
Total body weight (kg) 35 to 69kg
Hb < 100g/L = 1500mg
Hb 100-140g/L = 1000mg
Hb ≥ 140g/L = 500mg
Total body weight (kg) 70 or more
Hb < 100g/L = 2000mg
Hb 100-140g/L = 1500mg
Hb ≥ 140g/L = 500mg
Children
The calculator uses 15mg/kg per dose with up to two doses as per Powers JM et al (4)
Maximum 750mg per dose, maximum total dose of 1500mg.
In the study they gave two doses to those over 50kg, while for those weighing less than 50kg the decision for giving one or two doses was left up to the treating haematologist.
The age range was 9 months to 18 years
The calculation does not use the entered target or current haemoglobin.