Homocysteine is an amino acid formed as an intermediate when the body processes methionine from dietary protein. It is cleared by two routes that depend on folate and vitamin B12 on one side and vitamin B6 on the other, so the blood level reports on how well those pathways are running. It is also used as one marker of cardiovascular and thrombotic risk.
No readings for this marker yet.
Raised values most often reflect a shortage of folate, vitamin B12 or vitamin B6, and also occur with reduced kidney function, hypothyroidism, older age and inherited enzyme variants; markedly high levels in a young person raise the question of a rare metabolic disorder. Elevation is associated with a higher risk of atherosclerosis and venous clots, though it is a marker rather than a proven cause. Low values are of no clinical concern. An isolated raised result is a reason to repeat the test and review vitamin status with a doctor.
The sample must reach the laboratory promptly and be separated quickly, since red cells keep releasing homocysteine into standing blood and falsely raise the result; a protein-rich meal, smoking, coffee and impaired kidney function also push it up. It is interpreted alongside vitamin B12 and folate, which are the usual correctable reasons for elevation, and alongside kidney function.
Reference ranges are general adult values and depend on lab, assay, age and sex. For orientation, not diagnosis — discuss results with your doctor.