| Marker | Gabriel optimal | Typical lab range | Functional range |
|---|---|---|---|
| Homocysteine | 5 to 7 umol/L | 15 or lower | 5 to 7.2 |
What homocysteine is
Homocysteine is an amino acid your body makes while processing protein. Vitamin B12, folate and vitamin B6 help convert it into other substances, so levels normally stay low. When one of those steps is short, homocysteine builds up.
Labs may ask you to fast for 8 to 12 hours before the test. Tell your clinician about any B vitamin supplements, since they change the result. Gabriel's homocysteine lab guide covers the marker in more depth.
Normal and high levels
| Level (umol/L) | How it is usually described |
|---|---|
| About 5 to 15 | Typical lab range (varies by lab) |
| 15 to 30 | Mildly high |
| 30 to 100 | Moderately high |
| Above 100 | Severely high |
Gabriel's optimal band (5 to 7 umol/L) is tighter than the lab range. A result inside the lab range but above the optimal band is a prompt to check B12 and folate, not a diagnosis.
What causes high homocysteine
- Low vitamin B12, folate or B6. The most common cause. See the vitamin B12 blood test.
- Chronic kidney disease.
- An underactive thyroid. See the TSH blood test.
- Age, sex and menopause. Levels rise with age, are usually higher in men, and rise in women after menopause.
- Smoking.
- MTHFR variants. The MTHFR gene makes an enzyme that helps folate clear homocysteine. People with two copies of the common C677T variant tend to have higher homocysteine. It is common: both copies are found in about 10% to 15% of North American white people and about 25% of Hispanic people.
- Homocystinuria. A rare inherited disorder that causes very high levels.
For most people with MTHFR variants, links to disease are small and inconsistent, and most carriers never have related problems. See the MTHFR test and folic acid vs methylfolate guides.
What a high level means for your heart
Homocysteine that builds up can damage artery walls and raise the risk of blood clots, and high levels are linked to heart attack and stroke. But lowering homocysteine usually does not reduce heart attack or stroke risk, and routine screening isn't recommended for everyone.
So a high result is mainly a reason to find the cause, usually a B vitamin gap, and to work on the heart risks that matter most: not smoking, blood pressure, activity and cholesterol. It is also one of several inflammation and heart risk markers clinicians may check.
What to do with a high result
- Ask for B12, folate and MMA if they weren't checked, plus kidney and thyroid tests when they fit.
- Fix the cause, not just the number. If a B vitamin is low, your clinician can suggest how to replace it.
- Recheck after a change at the interval your clinician suggests.
- Ask about MTHFR testing only if it would change your care. A methylation panel bundles related markers.
High homocysteine itself causes no symptoms. See a clinician promptly for numbness or tingling, balance problems or memory changes, which can come from low B12. Call 911 for chest pain, sudden weakness on one side, trouble speaking, or a swollen, painful leg.
Common questions
What is a normal homocysteine level?
Most labs use about 5 to 15 umol/L. Gabriel's optimal band is 5 to 7 umol/L, a stricter target.
What causes high homocysteine?
Most often low vitamin B12, folate or B6. Kidney disease, an underactive thyroid, smoking, older age and MTHFR gene variants can also raise it.
Does MTHFR cause high homocysteine?
Two copies of the common C677T variant tend to raise homocysteine, but many carriers have normal levels, and links to disease are small and inconsistent.
Does lowering homocysteine reduce heart disease risk?
Usually not on its own. B vitamins can lower homocysteine, but that usually doesn't reduce heart attack or stroke risk, so focus on the cause and on proven heart habits.
Do I need to fast for a homocysteine test?
Often yes, for 8 to 12 hours. Follow your lab's instructions and mention any B vitamin supplements.
Sources
- Homocysteine Test MedlinePlus, U.S. National Library of Medicine
- Homocysteine Cleveland Clinic
- MTHFR gene MedlinePlus, U.S. National Library of Medicine (Genetics)
This guide is general information, not medical advice. It does not replace a visit with a licensed clinician. Gabriel membership is not health insurance.