- Choose Conventional (g/dL, kg) or SI (g/L, kg) units to match your CBC report. Switching units clears the hemoglobin fields.
- Enter the patient's body weight in kg. Use the post-dialysis dry weight for hemodialysis patients, not the inter-dialytic weight.
- Enter the current (actual) hemoglobin from the most recent CBC.
- Enter the target hemoglobin. For most dialysis patients use 10.0–11.5 g/dL (KDIGO 2012/2024); for non-dialysis CKD use 10.0–12.0 g/dL. The calculator requires target > actual Hgb.
- Select the route of iron replacement: IV iron sucrose for hemodialysis patients, oral iron for pre-dialysis CKD.
- Results show: total iron deficit in mg, estimated number of IV infusion sessions at 100 mg each, and the hemoglobin gap. Plain-language verdict and treatment protocol appear below the metrics.
All computation runs in your browser; no values are stored or transmitted.
When to Use
Use this tool when a CKD or dialysis patient has iron-deficiency anemia and you need to estimate the total amount of iron required to bring hemoglobin from its current value to a defined KDIGO target. It applies the Ganzoni formula — the standard pharmacokinetic method used to calculate IV iron sucrose dosing in renal anemia — and automatically divides the total deficit into individual 100 mg infusion sessions appropriate for the dialysis circuit.
Appropriate population
Adults with CKD G3–G5 or on maintenance hemodialysis or peritoneal dialysis who have confirmed iron-deficiency anemia (TSAT <20%, ferritin <100 ng/mL in non-dialysis CKD or <200 ng/mL in dialysis), a recent hemoglobin below the KDIGO target range, and a clinical indication for iron repletion. Most useful when preparing a cumulative IV iron sucrose prescription for the hemodialysis care team.
When NOT to use it
Do not use this calculator in patients who are iron-replete (ferritin >800 ng/mL or TSAT >30%) — the formula does not apply and further iron loading risks hemosiderosis and oxidative vascular injury. The calculator does not adjust for concurrent erythropoiesis-stimulating agent (ESA) use, ongoing blood loss, or functional iron deficiency (high ferritin with low TSAT in inflammation). Use the result as a starting estimate; recheck CBC and iron studies 4–6 weeks after completing repletion before prescribing a second course.
Pearls & Pitfalls
Check iron studies before prescribing
Always confirm iron deficiency with TSAT and ferritin before initiating IV iron. A low hemoglobin alone does not indicate iron deficiency — in inflammation, ferritin is elevated (acute-phase reactant) but TSAT may still be low (functional iron deficiency). The Ganzoni formula gives a total dose estimate; the treating physician must confirm the biochemical indication.
Use dry weight for dialysis patients
Hemodialysis patients accumulate several kilograms of fluid between sessions. Always use the post-dialysis dry weight (the weight at which the patient feels well with no signs of fluid overload) when calculating the iron dose — using the pre-dialysis or inter-dialytic weight will overestimate the deficit. Typical dry-weight targets are 0.5–1.0 kg above the estimated normovolemic weight.
Pitfalls
(1) Do not give IV iron if ferritin >800 ng/mL — iron overload from excessive repletion causes oxidative stress, endothelial injury, and increased infection risk. (2) The formula assumes no concurrent bleeding; if the patient has ongoing GI or dialysis-access bleeding, the calculated dose will be insufficient and must be re-estimated after the bleeding source is addressed. (3) IV iron sucrose infusions should be administered slowly (100 mg over 15 minutes into the venous return line, or over 30 minutes if given peripherally) to reduce the risk of hypotension and hypersensitivity reactions.
Why Use It
Iron deficiency is the most common correctable cause of anemia in CKD, affecting over 60% of predialysis patients and nearly all hemodialysis patients. Adequate iron stores are a prerequisite for the erythropoietic response to ESA therapy — without iron repletion, ESA doses escalate, costs rise, and hyporesponsiveness persists. The Ganzoni equation converts the hemoglobin gap and body weight into a total iron dose that accounts for both the circulating hemoglobin-bound iron deficit and a 500 mg depot reserve for bone marrow stores.
In hemodialysis patients, IV iron sucrose (iron sucrose — marketed as Ferrofer in the Philippines) is preferred over oral iron because intestinal absorption is severely impaired by hepcidin upregulation. IV iron delivered directly into the dialysis venous return line at 100–200 mg per session avoids gastrointestinal intolerance and achieves reliable tissue loading. The KDIGO 2012 Anemia Guideline and its 2024 update recommend IV iron for dialysis patients who are iron-deficient and on ESA, targeting ferritin 200–500 ng/mL and TSAT 20–30%.
Iron Deficit & IV Iron Dose — Ganzoni Equation
Enter body weight, current hemoglobin, target hemoglobin, and the intended route of iron replacement to calculate total iron deficit and infusion sessions.
⚕ Ganzoni formula: Iron deficit (mg) = Weight (kg) × (Target Hgb − Actual Hgb) × 0.24 + 500 (depot iron). Depot iron 500 mg is standard for replenishment; omit for maintenance dosing. IV iron sucrose (Ferrofer): standard infusion 100–200 mg per session. This is a dosing guide — actual prescribing requires physician authorization and consideration of ferritin, TSAT, and clinical status.
Next Steps
Use the result to support — not replace — clinical judgment.
- Interpret the value against the targets shown in the calculator and the Evidence section below, in the context of the full clinical picture.
- Trend serial measurements rather than acting on a single result; confirm abnormal or unexpected values before changing management.
- Apply the relevant KDIGO / specialty-guideline threshold and document the indication.
- Escalate or refer to nephrology when results are out of range, rapidly changing, or discordant with the clinical picture — and discuss the implications with the patient.
Evidence & References
Formula & Equations
| Quantity | Equation |
|---|---|
| Total iron deficit (mg) | Iron deficit = Body weight (kg) × (Target Hgb − Actual Hgb) × 0.24 + 500 |
| Hemoglobin iron constant (0.24) | Derived from: blood volume 70 mL/kg × Hgb iron content 3.4 mg/g × correction factor 1.0 = 0.24 mg iron per g/dL Hgb per kg body weight |
| Depot iron (500 mg) | Fixed addend to replenish bone marrow iron stores and prevent rapid re-depletion after repletion |
| Number of IV sessions at 100 mg/session | Sessions = ceil(Total iron deficit ÷ 100) |
KDIGO hemoglobin targets (2012 / 2024)
| Population | Hemoglobin target |
|---|---|
| Hemodialysis or peritoneal dialysis (on ESA) | 10.0–11.5 g/dL (100–115 g/L) |
| Non-dialysis CKD G3–G5 (on ESA) | 10.0–12.0 g/dL (100–120 g/L) |
| Iron repletion threshold — ferritin (HD) | Ferritin <200 ng/mL or TSAT <20% → give IV iron |
| Iron repletion threshold — ferritin (non-dialysis) | Ferritin <100 ng/mL or TSAT <20% → give iron (oral or IV) |
| Upper safety limit — do not give iron if | Ferritin >800 ng/mL regardless of TSAT |
The constant 0.24 in the Ganzoni formula is a rounded value; some authors use 0.2412 from the original 1970 paper. The 500 mg depot term is a consensus addend; KDIGO notes that this may need adjustment in patients who have received recent partial iron repletion. SI conversion: Hgb in g/L ÷ 10 = g/dL.
Evidence & References
The Ganzoni formula was first described in 1970 and remains the most widely used method to calculate parenteral iron dose for iron-deficiency anemia. Hemoglobin targets and iron repletion thresholds follow the KDIGO 2012 Anemia Guideline and its 2024 update, which specify ferritin and TSAT thresholds for initiating IV iron in CKD and dialysis patients. IV iron sucrose (Ferrofer) is recommended over oral iron in dialysis patients due to hepcidin-mediated suppression of intestinal iron absorption.
- Ganzoni AM. Eisen-Dextran intravenös: therapeutische und experimentelle Möglichkeiten. Schweiz Med Wochenschr. 1970;100(7):301–303.
- KDIGO Clinical Practice Guideline for Anemia in CKD. Kidney Int Suppl. 2012;2(4):279–335.
