Can this result diagnose a condition on its own?

No. Laboratory results are interpreted with symptoms, medical history, specimen conditions and related tests.

Which reference range should I use?

Start with the performing laboratory's own reference interval; clinical cutoffs, when relevant, are separate sourced thresholds used for a specific purpose.

When should I discuss the result with a healthcare professional?

Results that are clearly outside range, persistent, symptomatic or unexpected should be reviewed by a healthcare professional.

Information about a laboratory test

Homocysteine: What Does This Test Measure?

The Homocysteine test measures blood homocysteine influenced by vitamin B12, folate and B6 metabolism.

Test summary

Test name: Homocysteine
Abbreviations: tHcy, Homocysteine
Category: Functional Nutrient Biomarkers
Panel: Vitamin B12 / Folate Evaluation
Specimen: Plasma / serum
Common units: µmol/L

What does the test measure?

The Homocysteine test measures blood homocysteine influenced by vitamin B12, folate and B6 metabolism.

Why is the test ordered?

Used as a functional marker when B12, folate or B6 inadequacy is suspected and in selected clinical contexts; it is not a routine cardiovascular screening test for everyone.

Information about a low result

Low homocysteine is generally less clinically informative than an elevation and usually does not indicate a problem on its own.

Information about a high result

High homocysteine can be associated with B12/folate/B6 inadequacy, but kidney function, age, sex, thyroid status and other factors also affect it.

Reference and clinical context

Start with the performing laboratory's reference interval, unit, specimen type and method. Numeric information on this page is stored as sourced example intervals or clinical thresholds.

Reference context 1

> 15 µmol/L

Population: Adults / B12 assessment context
Age range: 18
Specimen: Serum / plasma

High homocysteine threshold used in B12 assessment

This is a sourced clinical-context threshold and should not be used alone as a diagnosis or treatment decision. The laboratory report and clinical context take priority.

Reference ranges may vary by laboratory, method used, age, sex, pregnancy status, and clinical context. The reference range on your own laboratory report takes precedence.

Interpretation notes

Homocysteine is not a specific vitamin test. An elevation alone does not establish a disease or treatment need.

Related specialties

Internal Medicine
Hematology
Gastroenterology
Family Medicine

Frequently asked questions

More information about this test

High Homocysteine: What Does It Mean?

Sources

Vitamin B12 – Health Professional Fact Sheet — NIH Office of Dietary Supplements
U.S. government nutrition reference · 2025 · Vitamin B12 status, serum B12, MMA and homocysteine interpretation · Verified: Aug 12, 2026
Folate – Health Professional Fact Sheet — NIH Office of Dietary Supplements
U.S. government nutrition reference · 2022 · Serum/RBC folate status and homocysteine context · Verified: Aug 12, 2026
Homocysteine Test — U.S. National Library of Medicine (MedlinePlus)
Government medical reference · 2025 · Homocysteine relation to B vitamins, confounders and testing limitations · Verified: Aug 12, 2026