- Choose a mode: "Predict ΔHgb from volume" (you have an order in mL and want the expected rise) or "Compute volume to reach target Hgb" (you want to back-calculate the mL needed).
- Enter weight (kg or lb), pick the age category (sets blood volume per kg: neonate 90, infant 80, child 75, adolescent/adult 70 mL/kg), and the patient's current Hgb in g/dL.
- Select the blood product (PRBC Hct ≈ 60% / whole blood ≈ 38% / reconstituted ≈ 51%, or enter a custom donor Hct). Hgb of the unit is taken as Hct ÷ 3.
- Enter the volume to transfuse (Mode A) or the target Hgb (Mode B). Result updates as you type and is colour-coded by severity.
For CKD, MDS, thalassemia, and other chronic anemias, restrictive thresholds (Hgb 7 g/dL; 8 g/dL with cardiac disease/ACS) apply — over-transfusing suppresses native erythropoiesis and worsens iron overload. All computation runs in your browser; no values are stored or transmitted.
When to Use
Use this calculator when ordering or planning a packed-red-cell or whole-blood transfusion — either to predict the expected post-transfusion Hgb rise from a planned volume (e.g., a paediatric 10 mL/kg order, or one adult unit), or to back-calculate the volume required to reach a target Hgb. It is built around the conservation equation ΔHgb × total blood volume = transfused volume × donor-product Hgb, with age-stratified blood-volume per kg.
Appropriate population
Adults and children receiving RBC transfusion for chronic anemia (CKD/ESKD on dialysis, MDS, thalassemia, sickle cell), peri-procedural anemia, or symptomatic acute blood loss after volume resuscitation. Especially useful in paediatric dosing (10–15 mL/kg per episode), in patients with HF/CKD where volume overload risk dictates conservative single-episode dosing, and in chronic transfusion-dependent patients where the formulary unit dose drives iron-overload trajectory.
When NOT to rely on it
This is an estimate — donor unit Hct, plasma volume changes, ongoing blood loss, splenic sequestration, hemolysis, and intravascular dilution can all move the actual post-transfusion Hgb away from the predicted value. Do not use it as a substitute for a measured post-transfusion CBC. It does not address transfusion indication; for chronic anemia, restrictive thresholds (Hgb 7 g/dL; 8 g/dL with cardiac disease/ACS) should drive the decision to transfuse at all (see ERI and ESA-dose tools first for CKD anemia).
Pearls & Pitfalls
Bedside rules of thumb
1 unit of adult PRBC ≈ 1 g/dL rise in a typical 70-kg adult. 10 mL/kg of PRBC ≈ 2–3 g/dL rise in a child. Donor-unit Hgb is taken as Hct ÷ 3 (PRBC ≈ 22 g/dL, whole blood ≈ 14 g/dL, reconstituted ≈ 17 g/dL). The calculator's verdict text shows the math (volume × product Hgb ÷ total blood volume) so you can audit it at the bedside.
Iron and the chronically transfused
One adult PRBC unit delivers ~200 mg of elemental iron. Patients on chronic transfusion (transfusion-dependent thalassemia, MDS, regularly transfused dialysis patients) accumulate iron predictably; pair every transfusion decision with a ferritin trend and consider chelation referral once ferritin trends > 1000 ng/mL or after ~20 lifetime units. Over-transfusion in CKD also suppresses endogenous erythropoiesis and may worsen ESA hyporesponsiveness.
Pitfalls
(1) Donor-unit Hct is variable (typically 55–70% for PRBC, lower for additive-solution units, higher for older units) — always check the actual ordered unit's label volume. (2) Infuse over 2–4 hours per unit; in CKD, HF, or the elderly, slow to 4 hours and consider IV furosemide 0.5–1 mg/kg between units if volume overload risk is high. (3) Post-transfusion Hgb is most reliable when drawn 15 min to 1 hour after the unit finishes (steady-state). (4) The formula does not account for ongoing blood loss; if the patient is actively bleeding, the predicted rise will overshoot reality.
Why Use It
Restrictive transfusion thresholds — Hgb 7 g/dL for stable patients, 8 g/dL with cardiac disease or acute coronary syndrome — are now the standard of care for adult inpatients, supported by TRICC, FOCUS, TRISS, and the 2016/2023 AABB guidelines. Yet day-to-day RBC ordering still often defaults to "two units" without estimating what one unit will actually do, or sizing the order to the patient's weight and pre-transfusion Hgb. This tool replaces that default with a one-screen quantitative check: this much donor Hgb, diluted into this estimated blood volume, will move the patient's Hgb by approximately this much. For paediatric dosing it formalizes the 10–15 mL/kg habit; for CKD and HF it surfaces the volume-overload risk that drives the 4-hour infusion and inter-unit diuretic; and for chronic transfusion-dependent patients it makes the cumulative iron burden visible early.
Transfusion Hemoglobin Predictor
Choose a mode, enter the patient's weight and current Hgb, pick the donor product, then enter either the volume to transfuse (Mode A) or the target Hgb (Mode B). The result reports the predicted ΔHgb (Mode A) or required volume in mL, mL/kg, and adult-unit estimate (Mode B), with a colour-coded safety check against bedside transfusion rules.
⚕ Estimate only. Donor unit Hct (typically 55–70% for PRBC), plasma-volume shifts, ongoing blood loss, hemolysis, and splenic sequestration can move the actual post-transfusion Hgb away from the predicted value. Always check the actual ordered unit volume on the label, infuse over 2–4 hours per unit (4 h in CKD/HF/elderly with inter-unit IV furosemide 0.5–1 mg/kg if volume overload risk), and verify with a post-transfusion CBC drawn 15 min–1 h after the unit completes.
Next Steps
Anchor every transfusion decision to a restrictive threshold and to the patient's underlying disease.
- Chronic anemia (CKD, MDS, transfusion-dependent thalassemia): restrictive threshold Hgb 7 g/dL (8 g/dL with cardiac disease or ACS); typical post-transfusion target Hgb 7–9 g/dL. Over-transfusing suppresses native erythropoiesis and accelerates iron overload (each PRBC unit ≈ 200 mg elemental iron).
- Sickle cell disease (simple transfusion): target ~10 g/dL; do not exceed because hyperviscosity worsens vaso-occlusion. For higher targets, switch to exchange transfusion (goal HbS < 30%).
- CKD / HF / elderly: infuse over 4 hours per unit, consider IV furosemide 0.5–1 mg/kg between units, and limit to one unit at a time with reassessment.
- Paediatric: usual dose 10–15 mL/kg PRBC per episode (give over 2–4 h). Volumes > 20 mL/kg in a single non-emergent transfusion risk acute volume overload — split into two episodes.
- For CKD anemia, transfusion should be a last resort: first optimize iron, then ESA — see ESA Resistance Index and ESA / EPO Dose Adjustment.
- Always confirm response with a post-transfusion CBC drawn 15 min–1 h after the unit completes.
Evidence & References
Formulae
| Quantity | Formula |
|---|---|
| Total blood volume (mL) | Weight (kg) × BVper kg (90 neonate · 80 infant · 75 child · 70 adolescent/adult) |
| Donor Hgb in unit (g/dL) | Donor Hct (%) ÷ 3 (PRBC ≈ 22 · whole blood ≈ 14 · reconstituted ≈ 17) |
| Mode A — Predicted ΔHgb (g/dL) | Volume (mL) × Hgbproduct ÷ Total blood volume (mL) |
| Mode B — Required volume (mL) | (Target − Current Hgb) × Total blood volume ÷ Hgbproduct |
| Adult-unit estimate | ceil(Volume ÷ 300 mL per PRBC unit) — reported for adults only |
Bedside cross-checks
| Rule | Use |
|---|---|
| 10 mL/kg PRBC ≈ 2–3 g/dL rise | Sanity-check Mode A in paediatric dosing. |
| 1 adult unit PRBC ≈ 1 g/dL rise in a 70-kg adult | Sanity-check Mode A in adults; expect lower rise in larger patients, higher in smaller. |
| 1 unit PRBC ≈ 200 mg elemental iron | Track cumulative iron in chronic-transfusion patients (chelation referral once ferritin trends > 1000 ng/mL or after ~20 lifetime units). |
| Post-transfusion CBC timing | 15 min – 1 h after the unit completes (steady-state). |
The conservation equation (donor red-cell mass distributes into the recipient's circulating blood volume) underlies both modes; bedside rules-of-thumb are empirical simplifications of this equation in typical patient sizes and donor-unit Hcts. Modern transfusion practice frames the indication against TRICC/FOCUS/TRISS-era restrictive thresholds rather than a fixed two-unit habit.
References
- Carson JL, Stanworth SJ, Dennis JA, et al. Transfusion thresholds for guiding red blood cell transfusion. Cochrane Database Syst Rev. 2021;12(12):CD002042. doi:10.1002/14651858.CD002042.pub5.
- Carson JL, Guyatt G, Heddle NM, et al. Clinical Practice Guidelines From the AABB: Red Blood Cell Transfusion Thresholds and Storage. JAMA. 2016;316(19):2025–2035. doi:10.1001/jama.2016.9185.
- Davenport RD. Pediatric transfusion. In: Simon TL, McCullough J, et al, eds. Rossi's Principles of Transfusion Medicine. 5th ed. Wiley; 2016.
- Kidney Disease: Improving Global Outcomes (KDIGO). Clinical Practice Guideline for Anemia in CKD. Kidney Int Suppl. 2012;2(4):279–335.
