What does a high Homocystein result mean?

Elevated homocysteine is a biomarker indicating disturbances in methionine metabolism. Common causes include deficiencies of vitamin B12, folate, or vitamin B6, as well as genetic variants such as MTHFR C677T (rs1801133), which can reduce enzyme activity. However, the effect of this variant is usually small—many individuals with one copy have normal homocysteine levels. Other causes include kidney disease, hypothyroidism, smoking, or certain medications. High homocysteine is considered an independent risk factor for cardiovascular disease, stroke, and thrombosis. Yet randomized trials have shown that lowering homocysteine with folic acid and B vitamins does not significantly reduce cardiovascular risk. Therefore, the clinical utility of screening or treatment remains debated. If homocysteine is elevated, a workup for underlying causes (e.g., vitamin status, renal function) is warranted. Routine methylfolate supplementation is not evidence-based unless a confirmed deficiency exists. Direct-to-consumer tests often overstate the importance of single gene variants. The evidence for association is strong (human-strong), but for intervention it is moderate. Safety note: High-dose folic acid can mask B12 deficiency.