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Living with Hyperhomocysteinemia

Higher than normal levels of homocysteine in the blood, which may be linked to artery disease and blood clots.

Understanding Hyperhomocysteinemia

Hyperhomocysteinemia means above-normal levels of homocysteine in the blood.

On its own, it may be linked to a higher risk of hardened arteries and repeated blood clots in arteries and veins, usually in the third or fourth decade of life. Raised homocysteine is also a feature of several inherited metabolic conditions, such as homocystinuria and MTHFR deficiency. It can also result from defects in vitamin B12 (cobalamin) use.

Signs & symptoms

GARD doesn't list specific symptoms for this condition yet.

Not everyone has every symptom. GARD's list comes from the Human Phenotype Ontology.

Diagnosis

  1. Talk with your doctor

    Share the symptoms you've noticed, when they started and your family health history. Notes and photos can help.

  2. See a specialist

    Your doctor may refer you to a specialist who knows rare conditions.

  3. Ask which tests can help

    Your care team will decide which exams and tests can confirm the diagnosis.

Care & treatment

Care team
A doctor familiar with rare conditions, plus specialists as needed
Expert care
Ask about multidisciplinary care centers for rare conditions
Treatment
GARD doesn't list specific treatments for this condition. Your care team will tailor care to your symptoms.
Research
Clinical trials and observational studies may be options. See the research section below.

General information, not medical advice. Your care team makes the decisions.

Everyday life

Living with a rare condition is easier with support.

  • Connect with rare disease patient organizations for support
  • Keep notes on symptoms, changes and questions for appointments
  • Ask about patient registries that help research
  • Look into financial aid and travel resources for care visits
Bring these questions to your next doctor visit
What is causing my high homocysteine level?
Does my clot or heart risk need extra checking?
Would genetic testing for CBS or MTHFR be useful?

Quick facts

High homocysteine is a feature of several inherited metabolic conditions. These include homocystinuria (CBS gene), MTHFR deficiency (MTHFR gene), and defects in vitamin B12 use.

Also known as: homocysteinemia

Patient organizations

Rare-disease groups that can help

Source: NIH GARD · HyperhomocysteinemiaGARD ID 8230 · GARD page updated September 2026 · Plain-language summary by Know Rare; editorial review pending. General information, not medical advice.

You are more than your diagnosis

Perspectives from people navigating life with Hyperhomocysteinemia.

Explore the Hyperhomocysteinemia blog

Explore research for Hyperhomocysteinemia

Explore actively recruiting Hyperhomocysteinemia studies with HealthSpark.

HealthSpark

Find actively recruiting studies for Hyperhomocysteinemia with HealthSpark. Share your city to explore research near you.

  • Recruiting studies from ClinicalTrials.gov
  • Share your city to look for research near you
  • Eligibility is confirmed by the study team

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Powered by HealthSpark, our AI chat helper · Study information from ClinicalTrials.gov · Eligibility is confirmed by the study team.

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