Homocysteine
- Sample Type
- Plasma
- Fasting
- Required
- Unit
- µmol/L
Function
Homocysteine is a sulfur-containing amino acid produced during the metabolism of methionine. Under normal conditions, homocysteine is quickly converted into other products with the help of Vitamin B12, Vitamin B6, and Folate. It serves as a critical junction point in the methylation cycle, which is essential for DNA synthesis and cellular repair.
Why it is Ordered
Homocysteine levels are measured to assess the risk of cardiovascular disease, stroke, and peripheral arterial disease. High levels are toxic to the lining of blood vessels and may promote blood clot formation. It is also used to screen for vitamin B12 or folate deficiencies, as homocysteine levels rise before these vitamins fall below their respective normal ranges. In infants, it is used to screen for the rare genetic disorder homocystinuria.
Associated Conditions
- Hyperhomocysteinemia: Elevated levels linked to atherosclerosis and venous thrombosis.
- B-Vitamin Deficiency: Specifically B12 (cobalamin) and B9 (folate).
- MTHFR Genetic Mutations: Variants like C677T can impair the body's ability to process folate, leading to higher homocysteine.
- Chronic Kidney Disease: Reduced clearance of homocysteine increases systemic levels.
- Cognitive Decline: High levels are associated with an increased risk of Alzheimer's disease.
Check Your Result
Check Your Result
Enter your lab result to see where you stand compared to the standard reference range.
Why Context Matters
Homocysteine is extremely sensitive to sample handling; if the blood is not centrifuged or refrigerated immediately after collection, the red blood cells will continue to produce homocysteine, causing a false elevation. Additionally, smoking, high coffee consumption, and several medications (like methotrexate or levodopa) can artificially raise levels. Fasting is mandatory, as a high-protein meal contains methionine which can transiently spike homocysteine levels.
Lab ranges are statistical averages, not biological laws. "Normal" for a 20-year-old male isn't normal for a 60-year-old female.
Clinical References
Source-of-truth databases and clinical guidelines for Homocysteine:
Official Sources
- Hyperhomocysteinemia - StatPearls - NCBI Bookshelfncbi.nlm.nih.gov
Research & Guidelines
- PubMed: Homocysteine Clinical GuidelinesNCBI / PubMed
Related Indicators
Medically Reviewed by Dr. Binoy Babu, MBBS
Board Certified Doctor • 10+ Years Clinical Experience
Dr. Babu is a practicing physician dedicated to empowering patients with clear, actionable medical information. He founded 2opi to bridge the gap between complex lab reports and patient understanding, ensuring everyone has access to a reliable second opinion.
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