Homocysteine is an amino acid your body uses to make protein and to build and maintain tissue. But excessive levels in your blood may increase your risk of stroke, certain types of heart disease, and disease of the blood vessels of the arms, legs and feet (peripheral artery disease). Your doctor may check your homocysteine level if you've had cardiovascular problems but don't have any of the traditional risk factors, such as smoking. Your doctor may also advise screening if any family members developed heart problems at a young age or have high homocysteine levels. Homocysteine levels may drop if you get plenty of folate (folic acid) and B vitamins in your diet through foods such as green, leafy vegetables and fortified grain products or through supplements. But it's not known if reducing your homocysteine level actually reduces your risk of death from cardiovascular disease, and the American Heart Association does not yet consider homocysteine a major risk factor for heart disease.