This test is intended for use in screening individuals who may be at risk for heart disease and stroke. Homocysteine is an independent risk factor for coronary heart disease. High blood levels may directly damage the delicate endothelial cells that line the inside of arteries and result in vascular inflammation, blood clot formation, and arterial plaque rupture. An 8 to 12 hour fast is required for this blood test. However, drink plenty of water and take medications as prescribed.