In gravitation, what is the approximate viscosity value of blood?

• A. 2-3
• B. 3-4
• C. 4-5
• D. 1-2

Answer: (B)

Viscosity is the resistance to flow, and blood is a suspension of cells in plasma, so its thickness depends on temperature and how many cells are present. At body temperature, whole blood typically sits in the 3 to 4 centipoise range. Plasma alone is thinner, around 1–2 cP, but the presence of red blood cells and their tendency to form aggregates raises the overall viscosity. Blood is also non-Newtonian, meaning its viscosity changes with how fast you try to push it; at low flow (low shear) it appears thicker, while at high flow (high shear) it becomes somewhat thinner as cells align and deform. Given these factors, 3–4 centipoise is the most representative value for physiological whole blood, making it the best choice. The other ranges are less typical: plasma alone is closer to 1–2 cP, and 4–5 cP would be higher than normal for most conditions.