When the body makes too much blood, it increases the number of red blood cells that make the blood too thick, increasing the risk of formation of blood clots, states the National Heart Lung and Blood Institute. Blood clotting blocks the circulation of blood in the arteries and veins, leading to stroke and heart attack. This situation occurs as a result of a rare blood disease called Polycythemia vera.
Thick blood tends to flow slowly in the body compared to the normal blood, says the National Heart Lung and Blood Institute. This slows the supply of oxygen to the vital organ of the body, resulting in several conditions such as heart failure and angina.
The bone marrow makes the red blood cells, which handles transportation of oxygen in the body and removal of carbon dioxide from the body cells to the lungs. When a Polycythemia vera occurs, the bone marrow makes too may red blood cells. The condition occurs when there is a mutation in the body's JAK2 gene, explains the National Heart Lung and Blood Institute.
The condition grows slowly in the body and may not show any symptoms. Doctors usually detect it when carrying out blood tests for other conditions. Signs may appear due to the increased thickness of blood.