Blood Colloid Osmotic Pressure Simulator

Explore how blood protein concentration affects water movement and blood volume

Normal
Proteins: 7.5 g/dL
Hydration: Normal
Dehydrated (Carlos)
Proteins: 8.2 g/dL
Hydration: Low
Overhydrated
Proteins: 6.8 g/dL
Hydration: High
Calculate Colloid Osmotic Pressure (COP)
COP = Protein Concentration × 3
👆 Click on a blood sample above to calculate its COP
Water Movement Across Capillary Wall
Click on a blood sample to see water movement

The Key Concept: Blood proteins (mainly albumin) create osmotic pressure that pulls water INTO blood vessels from tissues. Higher protein concentration = stronger pulling force.

Carlos' Situation: When he got dehydrated, he lost water from his blood, making his proteins MORE concentrated (8.2 g/dL instead of 7.5 g/dL). This increased COP should pull water back into his vessels... so why is his blood pressure LOWER?

The Answer: Timing! Carlos lost blood volume IMMEDIATELY when he didn't drink enough water. The elevated COP will help him recover volume, but that takes HOURS. His body can't pull water from tissues fast enough to make up for the acute volume loss. Result: Lower blood volume → Lower cardiac output → Lower blood pressure.