Ferric Carboxymaltose Dose Calculator
Ferric Carboxymaltose Dose Calculator
Work out the cumulative ferric carboxymaltose dose from body weight and haemoglobin using the simplified label table.
Ferric Carboxymaltose Dose
Weight + Hb → doseWeight 72 kg, haemoglobin 9.5 g/dL
Simplified dosing table
Hb ≥ 10 g/dL: 35–<70 kg → 1000 mg · ≥70 kg → 1500 mg
Hb < 10 g/dL: 35–<70 kg → 1500 mg · ≥70 kg → 2000 mg
- single dose limit
- 20 mg/kg and no more than 1000 mg in one administration
- interval
- at least 7 days between infusions
Worked example
Weight 72 kg, haemoglobin 9.5 g/dL
Hb below 10 g/dL and weight 70 kg or more → 2000 mg cumulative
Give as two 1000 mg infusions at least 7 days apart
Cumulative dose
| Haemoglobin | 35 to < 70 kg | ≥ 70 kg |
|---|---|---|
| ≥ 10 g/dL | 1000 mg | 1500 mg |
| < 10 g/dL | 1500 mg | 2000 mg |
Practical points
Ferric carboxymaltose delivers large amounts of iron in a short infusion, which is why it displaced the older preparations that needed a test dose and repeated small administrations. Dosing is by a simplified table keyed on body weight and haemoglobin rather than by the Ganzoni calculation, and the two do not always agree — the table is deliberately generous, on the basis that a modest excess is safer and more practical than under-replacement.
The important constraints are on the single dose rather than the total. No single administration should exceed 1000 mg or 20 mg/kg, and successive doses must be at least seven days apart. That is what turns a 2000 mg cumulative requirement into two visits.
Hypophosphataemia is the complication most often missed. Ferric carboxymaltose raises intact FGF-23 and causes renal phosphate wasting in a substantial minority of patients, occasionally severe and prolonged enough to cause osteomalacia. Check phosphate before repeat courses, particularly in patients receiving several doses over months, and consider an alternative preparation in anyone with a previous episode.
Frequently asked questions
What is the maximum single dose of ferric carboxymaltose?
1000 mg, and no more than 20 mg/kg. Larger cumulative requirements are split into separate infusions at least seven days apart.
Should I use Ganzoni or the simplified table?
The simplified table is what the product label specifies and what most units use. Ganzoni remains useful as a cross-check and for patients the table does not cover well.
Why check phosphate afterwards?
Ferric carboxymaltose raises FGF-23 and causes renal phosphate wasting. Hypophosphataemia is common, occasionally severe, and can persist for weeks — check before giving repeat courses.
How soon can haemoglobin be rechecked?
Allow at least four weeks. Ferritin drawn sooner is uninterpretable because the administered iron itself raises it.
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References
- Ferinject (ferric carboxymaltose) Summary of Product Characteristics.
- Wolf M et al. Effects of iron isomaltoside vs ferric carboxymaltose on hypophosphatemia. JAMA. 2020;323(5):432–43.