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Homocysteine

Cardiac profile Biomarker

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Collection Type: Blood

Body System

Related System: Cardiac profile

Overview

Homocysteine is an amino acid produced during methionine metabolism. The blood homocysteine test measures total plasma/serum homocysteine and helps assess risk for vascular disease and thrombotic disorders. Elevated levels are associated with increased risk of coronary artery disease, stroke, peripheral vascular disease and venous thrombosis; extremely high levels suggest inborn errors of metabolism (homocystinuria). Testing is considered when there is premature cardiovascular disease, unexplained thrombosis, recurrent pregnancy loss, or signs of B‑vitamin deficiency. Levels tend to rise with age, are generally higher in men than women, and fall in pregnancy; renal dysfunction and some medications also alter values.

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Test Preparation

No special preparation is required

Why Do I Need This Test

Profile: Cardiac profile (cardiovascular risk assessment).
Symptoms: Premature heart disease, stroke, unexplained blood clots, recurrent miscarriages, unexplained cognitive decline or neuropathy.
Diagnoses/monitoring: Assesses vascular/thrombotic risk, screens for vitamin B12/folate deficiencies and homocystinuria, monitors treatment response.
Reasons for abnormal levels: B‑vitamin deficiency (folate, B12, B6), renal impairment, genetic defects (e.g., MTHFR or CBS), certain drugs, hypothyroidism.
Biological meaning: Elevated homocysteine reflects impaired remethylation/transsulfuration and promotes endothelial dysfunction and thrombosis.
Lifestyle causes: Smoking, high caffeine/alcohol, high methionine diet, low vitamin intake.
Family history: Early/strong family history of premature CVD, recurrent thrombosis, or known homocystinuria.

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Understanding Test Results

<5 μmol/L (<0.07 mg/dL): Uncommon; may reflect high folate/B12 supplementation; rarely clinically significant.
5–15 μmol/L (0.07–0.20 mg/dL): Typical normal range; low-to-moderate cardiovascular risk.
15–30 μmol/L (≈0.20–0.41 mg/dL): Mild hyperhomocysteinemia; associated with modestly increased risk of atherosclerosis and venous thrombosis; evaluate B‑vitamin status, renal function, medications.
30–100 μmol/L (≈0.41–1.35 mg/dL): Moderate elevation; substantial vascular and thrombotic risk; requires workup for nutritional deficiencies, renal disease, hypothyroidism, and possible genetic causes.
>100 μmol/L (>1.35 mg/dL): Severe hyperhomocysteinemia, suggestive of inborn errors (e.g., homocystinuria) or severe metabolic/renal impairment; high risk of early thrombosis, lens dislocation and developmental issues—urgent specialist evaluation and treatment needed.
Elevated results are often correctable with folate, B6 and B12 replacement if deficiency is present; interpretation should account for age, sex, renal function and medications.

Normal Range

0.07-0.20 mg/dL OR 5-15 μmol/L

FAQs

Q: What happens when homocysteine is high?

A: High homocysteine damages blood vessel linings and promotes clot formation, raising risk of coronary artery disease, stroke and venous thrombosis. It’s linked to cognitive decline and higher risk of pregnancy complications (neural‑tube defects, preeclampsia). Common causes include deficiencies of folate, vitamin B12 or B6, genetic variants (e.g., MTHFR), kidney disease and some drugs. Treating causes and B‑vitamin supplementation can lower risk.

Q: Which foods reduce homocysteine?

A: Foods high in folate (leafy greens, legumes, fortified grains), vitamin B6 (potatoes, bananas, poultry), vitamin B12 (fish, meat, eggs, dairy, fortified cereals), and betaine/choline (beets, spinach, quinoa, wheat bran) help lower homocysteine. Regular intake of these—plus nuts and whole grains—supports homocysteine metabolism; consider a balanced diet or supplements if levels remain elevated.

Q: What are normal homocysteine levels by age?

A: Typical plasma total homocysteine ranges: infants/children ~3–7 µmol/L; adolescents ~4–11 µmol/L; adults (20–60 years) ~5–15 µmol/L; older adults (>60 years) often higher, commonly ~7–20 µmol/L. Levels >15 µmol/L are generally considered elevated and may warrant evaluation. Optimal target is often <10 µmol/L to lower cardiovascular risk; levels are influenced by diet and B‑vitamin status (B6, B12, folate).

Q: What is the function of homocysteine?

A: Homocysteine is a sulfur-containing amino acid that functions as an intermediate in methionine metabolism and the body’s methylation cycle. It is converted back to methionine (using folate and vitamin B12) or into cysteine (via vitamin B6-dependent transsulfuration). These pathways support methyl group transfers, glutathione production and amino acid balance; elevated homocysteine is linked to vascular and neurological risk.

Q: Can high homocysteine increase heart disease risk?

A: Yes. Elevated homocysteine is linked to higher cardiovascular risk: it can damage vessel linings, promote clotting and oxidative stress. Trials show B vitamins lower homocysteine but do not consistently reduce heart attacks or strokes. Managing established risks (blood pressure, lipids, smoking, diabetes) remains essential alongside addressing high homocysteine.

Q: Does vitamin B12 or folate deficiency cause high homocysteine?

A: Yes. Deficiencies of vitamin B12 or folate impair homocysteine remethylation to methionine, causing elevated homocysteine levels. Vitamin B6 deficiency also raises homocysteine by reducing transsulfuration to cystathionine. High homocysteine is linked to cardiovascular and neurological risks; correcting B12, folate (and B6) deficiencies typically lowers homocysteine and reduces related risk factors under medical guidance.