True. An increase in blood viscosity can cause an increase in total peripheral resistance (TPR). Blood viscosity is a measure of how thick and sticky the blood is, and it is determined by factors such as the number of red blood cells, plasma protein concentration, and shear rate. When blood viscosity increases, the blood flow through the blood vessels becomes more difficult, and this can lead to an increase in TPR. TPR is a measure of the resistance that the blood encounters as it flows through the systemic circulation and is an important determinant of blood pressure. An increase in TPR can cause an increase in blood pressure, which can have negative effects on cardiovascular health.