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Marker · Educational ranges, not diagnosis

Homocysteine

Also called tHcy.

A sulfur amino acid on the folate, B12, and B6 pathway. Blood levels fall when those vitamins go in, if the pathway was the problem.

Read this first

  • Coach, not doctor. Aaron Cuha is a coach, not a doctor. No clinical credential is claimed for him, or for these pages. A number on a panel is a conversation starter with a clinician, not a DIY diagnosis. Nothing here is a prescription, a protocol, or a reason to start or stop a medicine. Educational use only. This database summarizes published research and is not medical advice. Where a dose appears it is a record of what a trial or clinic ran, or what people describe doing, with its source attached. Nothing here is a recommendation for personal use.
  • Affiliate disclosure. Knowledge stays free. Every page, every guide and every tool is free to read and stays free. Lab-panel affiliate links, when they exist, live on /bloodwork/partners and print what is earned on the row, or that nothing is earned today. This glossary does not sell panels. The Archive does not order labs.
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Why a longevity audience asks

The owner's methylated-B rule waits on homocysteine, and only with MTHFR context. Large trials then showed that lowering homocysteine with B vitamins did not prevent vascular events. Moving the number is not the same as changing outcomes.

How a coach reads it

Many labs flag about 15 umol/L and above. Some prevention conversations prefer the low teens or under 10. Those are conversation ranges. HOPE-2 and NORVIT lowered the number and did not deliver the event benefit people expected.

Units on this page: umol/L

When it is low

Usually not a target. Very low values are uncommon and not a reason to add more B vitamins.

When it is high

Can mean low folate or B12, kidney disease, or a pathway variant. Check B12 with MMA before you celebrate a B-complex. MTHFR is context, not a protocol.

Easy ways to misread it

  • Lowering homocysteine is easy. Changing events was not, in the large trials.
  • Do not treat a high number with folate alone if B12 is undiagnosed. That can mask deficiency.

What to ask a clinician

Ask for homocysteine with serum B12, MMA, and folate. MTHFR testing is optional context, not a shopping list.

Related supplements

Related when-playbooks

Sources on this page