Díaz Lab Testing Store › Homocysteine | Serum (Quest) Image 1 of 1 Homocysteine | Serum (Quest) $67.00 Elevated homocysteine damages blood vessels and is linked to cardiovascular risk, B vitamin deficiency, and MTHFR variants. Add To Cart Added! Elevated homocysteine damages blood vessels and is linked to cardiovascular risk, B vitamin deficiency, and MTHFR variants. Add-on | Interpretation for Individual Markers $17.00 Add Added!