Homocysteine
Homocysteine is an amino acid produced during the metabolism of methionine (from dietary protein). It is normally recycled back to methionine via a process called methylation, which requires folate, vitamin B12, and vitamin B6 as cofactors. When these nutrients are deficient or methylation pathways are impaired, homocysteine accumulates.
Elevated homocysteine (hyperhomocysteinemia) is an independent risk factor for cardiovascular disease, stroke, and blood clots. It damages the endothelial lining of blood vessels and promotes oxidative stress and inflammation. It is also associated with cognitive decline and Alzheimer's disease.
Homocysteine is one of the most actionable biomarkers because elevated levels often respond to supplementation with methylated B vitamins (methylfolate, methylcobalamin, P-5-P) and dietary changes.
What It Measures
Homocysteine measures the blood level of this sulfur-containing amino acid. It serves as a functional marker of methylation pathway efficiency and B-vitamin status (folate, B12, B6).
Reference Ranges
| Status | Range (umol/L) |
|---|---|
| Optimal | < 7 umol/L |
| Normal | 7–10 umol/L |
| Borderline | 10–15 umol/L |
| Out of Range | > 15 umol/L |
Optimal Ranges
| Group | Range | Unit | Source |
|---|---|---|---|
| Standard | 0–15 | umol/L | Standard reference |
| Optimal | 5–10 | umol/L | Functional range |
When Values Are High
Elevated homocysteine is an independent cardiovascular risk factor and is associated with cognitive decline, depression, and osteoporosis. Often caused by B-vitamin deficiency (B12, folate, B6) or MTHFR genetic variants.
When Values Are Low
Low homocysteine is generally favorable and indicates efficient methylation. Very low levels (<4 umol/L) are rare and not clinically concerning.
What To Do
Lifestyle
- •Increase folate-rich foods (leafy greens, legumes)
- •Ensure adequate B12 intake (especially for vegans/vegetarians)
- •Limit alcohol which depletes B vitamins
Supplements
- •Methylfolate (5-MTHF) 400–800mcg if MTHFR variant present
- •Methylcobalamin (B12) 1000mcg sublingual
- •B6 (P5P form) 25–50mg
- •Trimethylglycine (TMG/betaine) if B-vitamins alone are insufficient
When to Retest
Retest 8–12 weeks after supplementation
How GATOR Tracks This
Lab Providers
Related Biomarkers
This content is for informational purposes only and does not constitute medical advice. Reference ranges may vary by laboratory and individual factors. Consult a qualified healthcare provider for interpretation of your results and treatment decisions.
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