Homocysteine optimal range and reference range
Compiled by Alina Radu, founder of Sera, from the published sources below · Last reviewed November 9, 2026
Sera's bands for Homocysteine:
- Optimal 0 – 9 μmol/L (0 – 9 nmol/mL); sufficient 9 – 12 μmol/L (9 – 12 nmol/mL); out of range above 12 μmol/L.
Evidence grade: Functional / longevity target. A narrower target in common use in functional, integrative, preventive and longevity practice. It is not a universally validated diagnostic range.
All units
| Unit | Optimal | Sufficient | Out of range |
|---|---|---|---|
| μmol/L | 0 – 9 | 9 – 12 | above 12 |
| nmol/mL | 0 – 9 | 9 – 12 | above 12 |
Bounded on the high side only — a low result is not treated as out of range. No evidence-based lower bound; the published thresholds all concern a raised homocysteine.
What the evidence says
Raised homocysteine can reflect low B12, folate or B6 status, or reduced kidney function. It rises with age and is higher in men. The acceptable band ends at 12 μmol/L, just above the 11 an international consensus treats as moderately raised. Laboratories commonly print a wider interval, to about 15. The optimal band ending at 9 is a functional target with no published threshold behind it. A low homocysteine is not flagged.
Sources
- Homocysteine and Dementia: An International Consensus Statement — Smith AD, Refsum H, Bottiglieri T, et al. — Journal of Alzheimer's Disease, 2018 · Peer-reviewed publicationTreats a plasma total homocysteine above 11 μmol/L as moderately raised and as a modifiable risk factor for cognitive decline in older people. Sera's acceptable band ends just above it, at 12.
What Homocysteine measures
An amino acid that reflects your B-vitamin status and a process called methylation.
High homocysteine can point to low B12 or folate and is linked to a higher risk of heart disease.