Converters
Jun 29, 2026
Why Blood Volume Is ~5 Litres and What That Number Explains About Shock, Donation Limits, and Surgery
Blood volume is approximately 5 litres (70 mL/kg) — which explains blood donation limits (450 mL is ~9%, safely within Class I shock threshold) and why haemorrhagic shock classes are defined where they are. Here's the complete lung volume framework (tidal, inspiratory reserve, residual — totalling ~5.8 litres), the 42-litre body water distribution across intracellular and extracellular compartments, and why gastric stretch receptor adaptation underlies persistent overeating patterns.