Homocysteine is an amino acid intermediary that's long been linked to cardiovascular and cognitive risk. Elevated values correlate with worse outcomes in observational data. Whether lowering it with B-vitamins actually improves outcomes is a separate — and less settled — question.
What homocysteine measures
An amino acid produced during the metabolism of methionine. Levels depend on folate, B12, and B6 status, kidney function, thyroid function, certain medications, and genetic variants (most famously MTHFR).
What the numbers mean
Reference ranges typically run up to ~15 μmol/L, with values under ~10 commonly cited as preferable by clinicians who track it. Very high values (>30) warrant a workup for specific causes.
Why the evidence is mixed
Observational studies consistently link elevated homocysteine to cardiovascular events and cognitive decline. Large randomized trials of B-vitamin supplementation to lower homocysteine have generally not produced the cardiovascular benefit the observational data predicted. The upshot: homocysteine is a useful marker, but "just take B-vitamins" isn't a proven fix for event risk. It's an honest area of open evidence.
What can move it
B12, folate, and B6 deficiency all raise it — and correcting deficiencies does lower the number. Kidney impairment, hypothyroidism, and some medications affect it. Lifestyle factors (smoking, coffee, alcohol) play smaller roles. Genetic MTHFR variants can influence processing.
How VisitRecall tracks it
Trend homocysteine alongside B12, folate, and kidney markers so the pattern is readable at your next visit. See lab tracking and the longevity hub.
FAQ
Should everyone test it?
Not a settled recommendation. Many preventive-focused clinicians order it; others don't. A conversation with your doctor about fit for your risk profile is reasonable.
If it's high, what do I do?
Assess for B12/folate/B6 deficiency, kidney and thyroid function, and context. Supplementation can lower the number, but its effect on hard outcomes is less clear than the correlation suggests.
Does MTHFR testing matter?
Common variants affect processing but aren't reliably predictive of health outcomes in isolation. Clinicians weigh it differently.
