Homocysteine
Homocysteine is an amino acid intermediate in methionine metabolism that is recycled with the help of folate, vitamin B12, and vitamin B6. Elevated levels damage blood vessel lining and promote clotting and are associated with higher risk of cardiovascular disease, stroke, and dementia. B-vitamin supplementation usually lowers homocysteine, though cardiovascular benefit in trials has been modest.
Units: µmol/L. Check the units on your report before comparing to any range here.
Optimal range: who says what
Institutions, researchers and practitioners draw the line in different places. Each position is listed with who holds it and, where a document states it, a link. How we verify ranges.
- Institution or study≤11 μmol/LInternational consensus on homocysteine and dementia (Smith et al. 2018)The consensus treats moderately raised homocysteine above 11 μmol/L as one cause of age-related cognitive decline and dementia
- Institution or studyLower is better; no thresholdHomocysteine Studies Collaboration meta-analysis (2002, JAMA)A 25% lower homocysteine (about 3 μmol/L) went with 11% lower ischemic heart disease risk and 19% lower stroke risk
- Named practitioner<7 μmol/L (optimal), <10.5 μmol/L (acceptable)Optimal DX · Homocysteine: Highs, Lows, and Optimals
- Named practitioner5-7.2 μmol/LDr. Hagmeyer · Best Blood Tests For Measuring Inflammation
- Named practitioner<12 μmol/L (<8 ideal)Life Extension · Lab Testing Protocol (Suggested Optimal Ranges)Disclosure: Life Extension sells lab panels that appear in our blood-test comparisons.
- Named practitioner6-9 μmol/L (target about 7)Tracey O'Shea (Kresser Institute) · Homocysteine: The Underordered Cardiovascular Risk Marker Your Patients Need You to Check
- Lab reference interval<15 μmol/LWhat a lab report flags against. A lab interval is not an optimal target.
Practitioner targets are individual positions, often tighter than guideline ranges. Each was checked against its article before publishing.
15 of 21 itemized panels
Inflammation & Immune Markers
What is Homocysteine?
Homocysteine is a sulfur-containing amino acid produced during the metabolism of methionine, an essential amino acid obtained from dietary protein. Normally, homocysteine is rapidly converted to other beneficial compounds through two pathways: remethylation (converting back to methionine using folate and vitamin B12) or transsulfuration (converting to cysteine using vitamin B6). When these pathways are impaired, homocysteine accumulates in the blood.
Elevated homocysteine (hyperhomocysteinemia) is associated with cardiovascular disease, stroke, and dementia in observational studies. Lowering it is easy: folate, B12, and B6 supplements reliably reduce homocysteine. Whether that prevents disease is a separate question. Large trials such as HOPE-2 and NORVIT lowered homocysteine without reducing heart attacks, and a Cochrane review of 15 trials found no effect on heart attacks or deaths. A modest reduction in stroke, about 10%, is the strongest benefit seen in trials.
Standard lab reference ranges usually run up to about 15 µmol/L. Lower targets used by some practitioners are listed with their sources in the ranges section. A high result is worth following up for B12 or folate deficiency, kidney disease, or genetic causes, and B vitamins will usually bring it down.
Why Homocysteine Matters for Longevity
- Cardiovascular disease: In prospective studies of healthy people, a 25% lower homocysteine (about 3 µmol/L) was associated with 11% lower heart disease risk and 19% lower stroke risk (Homocysteine Studies Collaboration 2002). Trials that lowered homocysteine with B vitamins did not reduce heart attacks, so it works as a risk marker more than a proven treatment target.
- Brain health: Elevated homocysteine is associated with cognitive decline and brain atrophy. In the VITACOG trial, B vitamins slowed brain atrophy in older adults with mild cognitive impairment, by 53% in those whose homocysteine was above 13 µmol/L.
- Methylation: Homocysteine sits at the junction of the methylation cycle, which depends on folate, B12, and B6. A high level often signals a shortfall in one of them.
- Pregnancy: Folic acid before and during early pregnancy prevents neural tube defects, which is why folate supplementation is standard care.
- All-cause mortality: Higher homocysteine is associated with higher mortality in observational studies, but lowering it with B vitamins did not reduce deaths in trials (Cochrane 2017, relative risk 1.01).
Interpretation bands (curated, PMID-backed)
Holder: OptimizeBiomarkers editorial synthesis of: Elevated homocysteine levels and risk of cardiovascular and all-cause mortality: a meta-analysis of prospective studies (Peng et al., 2015); Homocysteine and risk of ischemic heart disease and stroke: a meta-analysis (Homocysteine Studies Collaboration, 2002); Plasma homocysteine levels and mortality in patients with coronary artery disease (Nygård et al., 1997). No single paper sets these cutoffs; for attributed targets see who says what.
Optimal (Longevity)<7 µmol/L▼
- Exceptional homocysteine level associated with minimal cardiovascular risk and optimal methylation function
- This level is associated with lowest risk of cardiovascular events, dementia, and all-cause mortality
Good (Standard)7-10 µmol/L▼
- Adequate homocysteine level with acceptable cardiovascular and cognitive protection
- Some longevity practitioners target <8 µmol/L, but levels in this range are generally considered safe
Acceptable (Functional)10-12 µmol/L▼
- Mildly elevated homocysteine indicating methylation dysfunction
- Cardiovascular and dementia risk begin to increase significantly above 10 µmol/L
- B-vitamin supplementation recommended
Suboptimal (Standard)12-15 µmol/L▼
- Moderately elevated homocysteine associated with 20-40% increased risk of cardiovascular disease and stroke
- Clear indication for B-vitamin supplementation (folate, B12, B6) and investigation of underlying causes
What raises or lowers Homocysteine
Causes of high Homocysteine
- Folate deficiency (dietary insufficiency or malabsorption)
- Vitamin B12 deficiency (common in vegans, elderly, those with pernicious anemia or taking metformin/PPIs)
- Vitamin B6 deficiency (less common but important for transsulfuration pathway)
- MTHFR gene variants (C677T and A1298C are common and reduce the activity of an enzyme in folate metabolism)
- Kidney disease (impaired clearance of homocysteine)
- Hypothyroidism (low thyroid function impairs homocysteine metabolism)
- High methionine intake (excess animal protein consumption)
- Medications that deplete B vitamins (metformin, PPIs, H2 blockers, methotrexate, anti-seizure medications)
- Excessive coffee or alcohol consumption (depletes B vitamins)
- Smoking
Symptoms when Homocysteine is high or low
When high
Elevated homocysteine is usually asymptomatic until it causes disease. When very high (>30 µmol/L), may cause: premature atherosclerosis and cardiovascular disease in young adults, recurrent blood clots (deep vein thrombosis, pulmonary embolism), cognitive decline or dementia symptoms, peripheral neuropathy (tingling, numbness in hands/feet), psychiatric symptoms (depression, psychosis in severe cases), osteoporosis and fragility fractures. Note: Most people with homocysteine 10-20 µmol/L have no obvious symptoms but silently accumulating damage.
High: Often asymptomatic initially
When low
Homocysteine below 5 µmol/L is rare and not associated with any negative health effects. No symptoms or interventions needed.
Very low: Rare and not concerning
How to move Homocysteine
Effect sizes (how much something moves the marker) appear only where the paper cited under the item states them. Talk to your clinician before starting or changing any medication or supplement.
B-Vitamin Supplementation
Take methylfolate (5-MTHF) 1-5mg, methylcobalamin (B12) 1-5mg, and pyridoxal-5-phosphate (P5P, active B6) 50-100mg daily. Methylated forms skip the MTHFR step, so some clinicians prefer them for people with MTHFR variants; folic acid itself lowers homocysteine by about 25% in trials (Homocysteine Lowering Trialists 1998). This combination normalizes homocysteine in most people with a vitamin cause; retest after 8-12 weeks.
B-Vitamin Rich Foods
Eat folate-rich foods: dark leafy greens (spinach, kale), legumes (lentils, chickpeas), asparagus, broccoli. For B12: grass-fed beef, wild-caught fish, eggs, organ meats (liver). For B6: poultry, fish, potatoes, chickpeas, bananas. Note: Dietary changes alone rarely normalize elevated homocysteine; supplementation is usually needed.
Betaine/TMG Supplementation
Take trimethylglycine (TMG, also called betaine) 500-3000mg daily. TMG provides methyl groups directly and supports the remethylation pathway independent of folate and B12. Particularly helpful for those with MTHFR mutations or who don't respond fully to B vitamins alone. Start with 500mg and increase gradually.
Optimize Kidney Function
Homocysteine is partially cleared by the kidneys, so impaired kidney function (eGFR <60 mL/min/1.73m²) causes homocysteine elevation. Optimize kidney health through blood pressure control, adequate hydration, limiting nephrotoxic medications (NSAIDs), and managing diabetes if present. Even mild kidney dysfunction can significantly raise homocysteine.
Reduce Methionine & Support Thyroid
High dietary methionine (from animal protein) increases homocysteine production. While you don't need to avoid protein, consider moderating intake to 0.8-1.2g/kg body weight. Also check thyroid function (TSH, Free T4)—hypothyroidism impairs homocysteine metabolism. Treating hypothyroidism can significantly lower homocysteine.
Scientific Evidence
Homocysteine as a Risk Marker
An individual-data meta-analysis of 30 studies found that, in prospective studies of healthy people, a 25% lower homocysteine (about 3 µmol/L) was associated with 11% lower ischemic heart disease risk and 19% lower stroke risk. The authors concluded homocysteine is at most a modest independent predictor in healthy populations.
Source: Homocysteine and risk of ischemic heart disease and stroke: a meta-analysis.
B Vitamins and Cardiovascular Events
A Cochrane review of 15 trials (71,422 participants) found that lowering homocysteine with vitamins B6, B9 (folate), or B12 did not reduce heart attacks (relative risk 1.02) or deaths from any cause (1.01). Stroke was modestly reduced (4.3% versus 5.1%, relative risk 0.90).
Source: Homocysteine-lowering interventions for preventing cardiovascular events.
HOPE-2
In 5,522 patients with vascular disease or diabetes, five years of folic acid, B6, and B12 lowered homocysteine but did not reduce the combined rate of cardiovascular death, heart attack, and stroke (relative risk 0.95). Stroke alone was less frequent (relative risk 0.75), and hospitalization for unstable angina was more frequent.
Source: Homocysteine lowering with folic acid and B vitamins in vascular disease.
NORVIT
In 3,749 patients treated within a week of a heart attack, folic acid plus B12 lowered homocysteine by 27% but did not reduce recurrent heart attack, stroke, or sudden coronary death. The folic acid, B12, and B6 combination showed a trend toward harm (relative risk 1.22).
Source: Homocysteine lowering and cardiovascular events after acute myocardial infarction.
B Vitamins and Brain Atrophy
In the VITACOG trial, 271 adults over 70 with mild cognitive impairment took folic acid, B12, and B6 or placebo for 24 months. Brain atrophy slowed from 1.08% to 0.76% per year, and by 53% in those with baseline homocysteine above 13 µmol/L.
Which Providers Test Homocysteine?
Cheapest: Mito Health at $297/year. Most comprehensive: Function Health, 160+ biomarkers for $365/year.
15 panels that include it, cheapest first
| Provider | Annual Cost | Total Biomarkers | $/Biomarker |
|---|---|---|---|
| $297 | 100+ | $2.97 | |
 Superpower | $349 | 100+ | $3.49 |
| $349 | 75+ | $4.65 | |
 WHOOP Advanced Labs | $349 | 65 | $5.37 |
 Function Health | $365 | 160+ | $2.28 |
| $365 | 100+ | $3.65 | |
| $375 | 108 | $3.47 | |
| $495 | 80+ | $6.19 | |
| $499 | 100+ | $4.99 | |
| $700 | 138 | $5.07 | |
| $895 | 100+ | $8.95 | |
| $996 | 59 | $16.88 | |
| $1188 | 70+ | $16.97 | |
| $1198 | 40+ | $29.95 | |
| $1950 | 130+ | $15.00 |
$/Biomarker is annual cost divided by the panel's advertised biomarker count, not the price of this one test. We track 23 blood test providers (32 plans); 21 of those plans are itemized marker by marker. Compare all of them.
6 itemized panels do not include Homocysteine
Labcorp OnDemand · Everlywell · InsideTracker · Marek Health Base · Empirical Health · Oura Health Panels
11 providers not itemized in our matrix
We have not itemized these marker by marker (some sell tests one at a time), so this page cannot say whether they offer Homocysteine. Check with them directly.
Life Extension Standard · Quest Health · Ultrahuman Blood Vision · Lifeforce · Hundred Health · Personalabs · Walk-In Lab · HealthLabs · WHOOP Specialized Panels · Marek Health Essential · Vitality Blueprint Upload
Experts discussing Homocysteine
Podcast episodes where clinicians and researchers cover this marker in depth. Curated by hand; an episode is listed only when the marker is a substantial topic, not a passing mention.
- Dr. Rhonda Patrick: Micronutrients for Health & LongevityDisclosure: Huberman Lab has been sponsored by Function Health, which appears in our blood-test comparisons.
- How Metabolism Works & The Truth About Inflammation
- Personalize Your Nutrition Based on Genetics
Frequently Asked Questions
What is the optimal range for Homocysteine?
Published positions differ: ≤11 μmol/L (International consensus on homocysteine and dementia (Smith et al. 2018)); Lower is better; no threshold (Homocysteine Studies Collaboration meta-analysis (2002, JAMA)). Named practitioners target: <7 μmol/L (optimal), <10.5 μmol/L (acceptable) (Optimal DX); 5-7.2 μmol/L (Dr. Hagmeyer); <12 μmol/L (<8 ideal) (Life Extension); 6-9 μmol/L (target about 7) (Tracey O'Shea (Kresser Institute)). Lab reference interval: <15 μmol/L. That is what a lab report flags against, not an optimal target.
Which blood test providers include Homocysteine?
15 of the 21 blood testing panels we itemize marker by marker include Homocysteine in their panels. This biomarker is widely available across major providers.
Related: YouBoost rates lifestyle and supplement interventions by evidence; HRV Zone tracks recovery trends.
Medical Disclaimer
This information is for educational purposes only and is not medical advice. Always consult with a qualified healthcare provider about your specific health needs.
Last reviewed Sep 23, 2026 · First published Sep 30, 2025