Higher viscosity of blood will increase the amount of stress placed on the heart while it is pumping. viscosity of blood is highest when _

The viscosity of blood is highest when hematocrit is higher.

Hematocrit is termed as the volume percentage of red blood cells which is in blood. Hematocrit is the most considered integral parts of person's complete blood count which results together with hemoglobin concentration.

 Platelets and white blood cells also count. The work of red blood cells is to transfer oxygen from lungs to all other parts of the body tissues and to samples of blood of hematocrit.

Viscosity is defined as the ability of a fluid to resist flow. Viscosity of the blood is increased if the hematocrit is increased. Hematocrit is defined as the proportion of red blood cells to the total volume of blood. Hematocrit can be increased by conditions such as polycythemia vera (increased production of red blood cells) and dehydration (decrease in plasma volume).

Viscosity of the blood is determined by the hematocrit, red blood cell aggregation and deformability, and plasma viscosity with the hematocrit being the most important. 

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