Allowable Blood Loss

Maximum allowable blood loss from weight and haemoglobin.

Patient

Weight (kg)

Initial Hb (g/dL)

Minimum acceptable Hb (g/dL)

EBV = weight × blood-volume factor. ABL = EBV × (initial − minimum Hb) ÷ initial Hb. Education only — transfusion thresholds and blood-volume estimates must follow local protocol and the clinical picture.

Maximum allowable blood loss

2250

Estimated blood volume

5250 mL

75 mL/kg × 70 kg

Maximum allowable blood loss

Allowable blood loss (ABL) estimates how much blood a patient can lose before reaching a minimum acceptable haemoglobin, helping plan transfusion and fluid strategy in surgery.

How it is calculated

Estimated blood volume (EBV) = weight × a blood-volume factor (about 75 mL/kg adult male, 65 female, 70 child, 80 infant). ABL = EBV × (initial − minimum Hb) ÷ initial Hb.

When it helps

Useful before liposuction, large flap or body-contouring surgery to set a transfusion trigger and guide intraoperative fluid replacement.

Education only — an estimate; transfusion decisions depend on the whole clinical picture and local protocol.