What is homocysteine?
A homocysteine test is a blood test. It measures the amount of homocysteine, an amino acid in the body. The test is often used to diagnose vitamin B6, B9 or B12 deficiency. People with elevated homocysteine may have a higher risk for cardiovascular disease. In newborns, homocysteine testing can help diagnose a rare condition called homocystinuria.