Markers · Cardiovascular
A homocysteine of 13, inside the lab's range. Homocysteine, read against the rest of you.
What homocysteine measures, what it does in the body, why it's tested, and the two ranges it's read against. Everything said about the marker here comes from Merlin's own biomarker catalogue.
What homocysteine is
Homocysteine is a sulfur-containing amino acid produced during the metabolism of methionine, an essential amino acid obtained from dietary protein. Elevated homocysteine levels (hyperhomocysteinemia) indicate impaired methylation pathways, often due to deficiencies in B vitamins (B6, B9, B12) or genetic variants such as MTHFR mutations. High levels are associated with increased risk of cardiovascular disease, stroke, cognitive decline, and endothelial dysfunction.
What it does in the body
Homocysteine is an intermediate in the methionine cycle, where it is either remethylated back to methionine (requiring folate and B12) or transsulfurated to cysteine (requiring B6). This process is central to the one-carbon metabolism pathway, which supports DNA methylation, neurotransmitter synthesis, glutathione production, and overall cellular methylation capacity. Dysregulation leads to oxidative stress, endothelial damage, and increased thrombogenicity.
Why it's tested
Homocysteine testing is used to assess cardiovascular disease risk, evaluate B-vitamin status (B6, B9, B12), investigate unexplained thrombosis, screen for MTHFR gene variants, and monitor cognitive decline or dementia risk. It is also used to guide supplementation therapy and track treatment response in patients with elevated baseline levels.
The two ranges
The reference range reflects population statistics. The target reflects physiology.
- Lab reference range
- 5-15 µmol/L (normal reference); >15 µmol/L considered hyperhomocysteinemia
- Functional target
- < 12 µmol/L
Those are different numbers, and you deserve to know which one you're looking at. Merlin reads your result against both.
Where this lives
A Field Guide to Atherosclerotic Risk
The field guide that covers homocysteine in depth, whole and public.
In a real read
Homocysteine is in the real Cardiovascular read on this site at 7.7 umol/L, where the read calls the endothelial axis "clean". It's also one of the markers tagged to retest in three months, so the next draw shows whether it held.
A real Cardiovascular surface from a real anonymized panel: the score, the narrative, the layers underneath. Yours will be built the same way, on your own numbers.
Educational context for your conversations with your licensed healthcare provider, not a diagnosis or a treatment plan. Merlin reads results; it doesn't diagnose.
No homocysteine result yet? You can order it inside Merlin: it's on Heart Health Essentials ($100) and Merlin Core ($180).
Bring the panel this number came from. Merlin reads it against everything else you have, every system and every year, then shows you what it means and what's worth finding out next. Start with your first month.