Lab test
What is a homocysteine test, and what are normal levels?
A homocysteine test measures an amino acid that the body normally breaks down using vitamins B12, B6 and folic acid, so a high level can reflect a shortfall in those vitamins. It is also used in heart risk and rare genetic conditions. Labcorp lists 0.0 to 14.5 µmol/L for adults aged 18 to 60.
What does the homocysteine test measure?
Homocysteine is an amino acid. The body uses vitamin B12, vitamin B6 and folic acid to break it down, so levels are normally low. MedlinePlus
Why is the homocysteine test ordered?
- Most often to look at vitamin B6, B12 and folic acid status, since a shortfall in any of them can raise homocysteine. MedlinePlus
- To help diagnose homocystinuria, a rare genetic disease. MedlinePlus
- High levels may be linked to a higher risk of heart disease, stroke or other blood vessel disorders. MedlinePlus
What are typical homocysteine ranges?
Labcorp publishes homocysteine ranges that rise with age. Labcorp
Reference ranges differ between laboratories and testing methods, and many also differ by age, sex, pregnancy or the phase of the menstrual cycle. The range printed on your own report is the one that applies to your result, and a clinician interprets it alongside your history.
| Age | Reference range |
|---|---|
| 18 to 60 years | 0.0 to 14.5 µmol/L |
| 61 to 70 years | 0.0 to 17.2 µmol/L |
| 71 to 80 years | 0.0 to 19.2 µmol/L |
| Over 80 years | 0.0 to 21.3 µmol/L |
What can affect homocysteine results?
- You may need to fast for 8 to 12 hours; some medicines and supplements, especially B vitamins, can affect results. MedlinePlus
- Labcorp prefers a fasting specimen to establish baseline values. Labcorp
- Higher levels also occur with osteoporosis, chronic kidney disease and hypothyroidism. MedlinePlus
When should you talk to a clinician about a homocysteine result?
- A high result does not always mean a condition that needs treatment; ask the clinician who ordered it whether more tests, such as B12 or folate, are needed. MedlinePlus
DiscoverMedica explains what a test measures and what named sources publish. It does not interpret individual results; the clinician who ordered your test, or one you choose, does.
Where can you get a homocysteine test?
A clinician can order it as part of routine or follow-up care. Some services also let you order lab tests yourself; check that a service’s panel includes this marker, which laboratory runs it, and who reviews the result with you.
- Function HealthAnnual membership for broad lab panels, drawn at Quest sites or at home.
- Quest HealthOrder individual lab tests from Quest Diagnostics online, without a doctor’s visit.
Homocysteine Test: questions, answered
What is a normal homocysteine level?
Labcorp lists 0.0 to 14.5 µmol/L for adults aged 18 to 60, rising to 0.0 to 17.2 at 61 to 70, 0.0 to 19.2 at 71 to 80 and 0.0 to 21.3 over 80. Other laboratories may differ, so compare results with the range on your report.
What causes high homocysteine?
MedlinePlus lists not getting enough vitamin B12 or folic acid, the genetic condition homocystinuria, and conditions such as chronic kidney disease, hypothyroidism and osteoporosis. A high value can also be linked to a higher risk of heart and blood vessel disease. A clinician decides what further testing makes sense.
Do I need to fast for a homocysteine test?
Often. MedlinePlus says you may need to fast for 8 to 12 hours, and Labcorp prefers a fasting specimen. Tell the person ordering the test about any vitamins you take. Mention vitamin B12, B6 and folic acid supplements in particular, because MedlinePlus notes B vitamins can affect the result.
Sources
Last reviewed October 7, 2026. Every source above was checked on or before that date. Educational information only, not medical advice; it does not replace a conversation with a licensed clinician. DiscoverMedica does not employ clinicians.