The homocysteine blood test helps diagnose B12/folate deficiencies, homocystinuria in infants and to identify patients who may be at risk for heart disease and/or strokes.Patients are advised to fast for 10-12 hours prior to the homocysteine blood test. Results are available in one to two days. This online blood test is a cheap, convenient and confidential alternative for people without a doctor’s order or for those with no insurance.Homocysteine is an amino acid that can be linked to several vitamins like folic acid, B6 and B12. Deficiencies of these vitamins may cause elevated levels of homocysteine. Research suggest that people with elevated homocysteine levels have a much greater risk of heart attack or stroke than those with normal levels. Additionally, increased concentrations of homocysteine have been linked to an increase in blood clots, which can lead to strokes, heart attack and blood vessel blockages in any part of the body.