homocysteine

noun

ho·​mo·​cys·​te·​ine ˌhō-mō-ˈsi-stə-ˌēn  ˌhä- 

: an amino acid C₄H₉NO₂S that is produced in animal metabolism by the demethylation of methionine and that appears to be associated with an increased risk of cardiovascular disease when occurring at high levels in the blood

Examples of homocysteine in a Sentence

Recent Examples on the Web

Supports Brain Health Having low levels of B12 can increase homocysteine, which can cause nerve cell inflammation and oxidative stress. —Jillian Kubala, Health, 22 Apr. 2026

One risk factor for atherosclerosis is homocysteine, an amino acid naturally found in the body that can contribute to artery damage and blood clotting if its level rise too high. —Mara Santilli, Flow Space, 5 Feb. 2026

Helps Protect Your Heart and Blood B12 helps break down homocysteine, an amino acid in the blood. —Jennifer Lefton, Verywell Health, 5 Nov. 2025

Word History

Etymology

International Scientific Vocabulary hom- + cysteine

First Known Use

1932, in the meaning defined above

Medical Definition

homocysteine

noun

ho·​mo·​cys·​te·​ine ˌhō-mō-ˈsis-tə-ˌēn  ˌhäm-ō- 

: an amino acid C₄H₉NO₂S that is produced in animal metabolism by the demethylation of methionine and forms a complex with serine that breaks up to produce cysteine and homoserine and that appears to be associated with an increased risk of cardiovascular disease when occurring at high levels in the blood