What percentage of blood is made up of water?

• A. 83%
• B. 70%
• C. 60%
• D. 90%

Answer: (A)

The key idea is that blood is a mixture of plasma and formed elements, and plasma is the watery part of blood. Plasma is about 92% water, but when you account for the cellular components that make up the rest of blood, the overall water content of whole blood averages roughly 83%. That’s why 83% is the best representation. The higher figure would imply almost pure liquid plasma, while the lower figures ignore how much water plasma contributes and how the cellular parts dilute that water content. Water in blood acts as the main solvent and transport medium, helping to carry nutrients, wastes, and other molecules throughout the body.