High Homocysteine: What It Is, Why It Matters, and How to Lower It

Homocysteine is an amino acid your body produces naturally as a byproduct of metabolising methionine. In a healthy methylation cycle, homocysteine is efficiently converted back into beneficial compounds. When this conversion is impaired — due to MTHFR gene variants, B vitamin deficiency, or lifestyle factors — homocysteine accumulates to levels that damage blood vessels, nerves, and brain tissue.

What Is a Normal Level?

Normal homocysteine is generally considered below 10 µmol/L. Borderline elevated is 10–15. Elevated is 15–30. Severely elevated is above 30. Some functional medicine practitioners consider anything above 7–8 µmol/L suboptimal for long-term brain health.

What Causes High Homocysteine?

The most common causes are MTHFR gene variants that impair the methylation cycle, deficiency in folate, B12, or B6, excessive alcohol consumption, smoking, chronic kidney disease, certain medications including methotrexate and some anticonvulsants, and ageing.

Why High Homocysteine Matters

Elevated homocysteine is independently associated with cardiovascular disease and stroke, Alzheimer's disease and cognitive decline, depression and anxiety, neurological damage and peripheral neuropathy, blood clotting disorders, and pregnancy complications. The VITACOG trial found that B vitamin supplementation reduced brain atrophy rate by 53% in people with mild cognitive impairment and elevated homocysteine.

How to Lower Homocysteine

The most evidence-based approach is supplementation with the three key methylation B vitamins in their active forms: methylfolate (5-MTHF), methylcobalamin, and P-5-P (active B6). TMG (trimethylglycine) supports the alternative betaine pathway for homocysteine clearance. Reducing alcohol, smoking, and excessive coffee intake also helps. Testing homocysteine before and after supplementation is the best way to confirm the intervention is working.

NeuroThrive™ products are food supplements and are not intended to diagnose, treat, or cure any medical condition. If you have elevated homocysteine, please work with your GP.