Our blood consists of many components, i.e., red blood cell, white blood cell, ...

To do it's role in the body, blood should have small viscosity. Which viscosity is the suitable range value in the our body blood vessel?

And, which way can we measure blood viscosity similar to the human vessel condition?

The normal blood viscosity at room temperature is around 10 cP (centipoise). This is about three times higher than that of pure water, reflecting the amount of red blood cells and proteins in the blood. High viscosity is related to polycythaemia, low viscosity to anaemia.

Another factor to consider in increasing blood viscosity is hyperglycemia.

If viscosity of the blood is increased, the flow through the micro-vessel will not be easy.

It makes the mass transfer problem , i.e., the transfer of oxygen, carbon dioxide, nutriments and waste product.

The flow through the micro-vessel is controlled by the viscosity, micro vessel diameter, micro-vessel elasticity and micro-vessel length, and connectivity.

Some researcher states that red blood cell figure is important, too. It looks like donut's format.

Then, is the micro vessel size alway constant through the human life?