High homocysteine levels in the blood can damage the lining of the arteries. High levels may also make the blood clot more easily than it should. This can increase the risk of blood vessel blockages. A clot inside your blood vessel is called a thrombus. A thrombus can travel in the bloodstream. From there, it can get stuck in your:
Lungs (called a pulmonary embolism).
Brain (which can cause a stroke).
Heart (which can cause a heart attack).
I’m honestly not too sure about this because of this not being English
Blood Provides the Body's Cells with Oxygen and Removes Carbon Dioxide. Blood absorbs oxygen from air in the lungs. It transports the oxygen to cells throughout the body, and it removes waste carbon dioxide from the cells.