Homocysteine is an intermediate produced while the methylation cycle is running. When methylation is flowing, it gets converted onward without trouble; when the conversion is stuck, it accumulates in the blood — which makes it a very useful marker of how efficiently methylation is working.
What is homocysteine?
Your body runs methylation every day: a reaction that moves methyl groups around, involved in DNA repair, neurotransmitter synthesis, hormone metabolism and detoxification. Homocysteine is produced partway through that cycle, and under normal conditions it is recycled or metabolized away.
If you think of methylation as a production line, homocysteine is the stock piling up in the work-in-progress area. Little stock means the line is running; stock piling high means something along the way is stuck.
What causes high homocysteine?
The reasons for the build-up almost all point to the same thing: not enough of the raw materials or enzymes the conversion needs.
| Common cause | Explanation |
|---|---|
| Low B vitamins | B6, B12 and folate are the key cofactors for converting homocysteine; a shortfall in any one of them stalls the process |
| MTHFR genotype variation | Affects how efficiently folate is activated; people carrying certain variants have a higher requirement for the active form |
| Low choline / betaine intake | The raw material for the backup conversion pathway |
| Declining kidney function | Slower metabolic clearance |
| Certain medications and lifestyle factors | Some medications, smoking and excessive alcohol are all associated with higher values |
What does high homocysteine mean for you?
Research has observed over the long term that elevated homocysteine is associated with changes in vascular endothelial function, cognitive function and bone metabolism. It is worth stressing that these are epidemiological associations — it works more like a warning light telling you methylation is not running smoothly at the moment, rather than a single number from which conclusions can be drawn.
High homocysteine is not itself the cause; it is the result. What you actually need to find is which stage is stuck — the active forms of B6, B12 and folate, MTHFR genotype, and kidney function all need to be read together before that can be determined.
See which systems the 136 markers cover →How do you lower homocysteine?
🍽️ Restore the raw materials through diet
- Folate: dark green vegetables, legumes, asparagus
- B12: mainly animal-based sources (meat, eggs, dairy, shellfish); vegans need to pay particular attention
- B6: salmon, chicken, bananas, chickpeas
- Choline / betaine: egg yolk, beetroot, quinoa
💊 With supplements, the form matters more than the dose
- People carrying certain MTHFR variants differ in how efficiently they use the active forms of folate (5-MTHF) and B12 (methylcobalamin)
- Whether you need to supplement at all, and which form to use, depends on your genotype and your existing data. That falls within the scope of a one-to-one consultation, and we do not give dosage advice here
🚭 Lifestyle
Smoking and excessive alcohol are both associated with rising homocysteine, while regular exercise is associated with lower values. This part is the foundation and applies to everyone.
Frequently asked questions
What is homocysteine?
Homocysteine is an amino acid produced partway through the methylation cycle. Under normal conditions B6, B12 and folate help convert it onward; when that conversion does not run smoothly it accumulates in the blood, which is why it is often used to assess how efficiently methylation is working.
What causes high homocysteine?
The most common causes are low B6, B12 or folate, or an MTHFR genotype that affects how efficiently folate is activated. Other causes include low choline and betaine intake, declining kidney function, certain medications, smoking and excessive alcohol.
How do you lower homocysteine?
The direction is to restore the raw materials the conversion needs: dark green vegetables and legumes (folate), animal-based foods (B12), salmon and bananas (B6), egg yolk and beetroot (choline, betaine), alongside adjusting smoking and drinking habits. Where MTHFR genotype is involved, the form you choose affects how well you can use it.
How are methylation and homocysteine related?
Methylation is the reaction by which the body moves methyl groups around, and it is involved in DNA repair, neurotransmitter synthesis and detoxification. Homocysteine is an intermediate in that cycle: the more it accumulates, the more it usually indicates that some stage of methylation is not running smoothly.
Should I test homocysteine, and what should go with it?
Testing homocysteine alone tells you the result but not the cause. It is usually read alongside the active forms of B6, B12 and folate plus MTHFR genotype, which is what allows you to work out where the hold-up is and what to address.
Want to know where your methylation is getting stuck?
Homocysteine only tells you that something is not running smoothly; it will not tell you why.
Body Decode, 136 markers, covers 17 health categories including nutrients, metabolic and detoxification, with a 60-minute consultant report review and a 120-day action plan.
