Hyperhomocysteinemia or hyperhomocysteinaemia is a medical condition characterized by an abnormally high level of homocysteine in the blood, conventionally described as above 15µmol/L.
As a consequence of the biochemical reactions in which homocysteine is involved, deficiencies of
vitamin B6, folic acid (vitamin B9), and vitamin B12 can lead to high homocysteine levels.