Homocysteine

CardiovascularMeasured in µmol/L

What it measures

An amino acid intermediate whose concentration reflects folate, B12, and B6 status as well as kidney function and genetics.

Why it matters

Markedly elevated values can indicate B-vitamin deficiency or an inherited metabolic disorder worth identifying.

Where the claimed ranges actually sit

Measured in µmol/L. Each row is one claim about where your result should fall.

What a laboratory reportsWhat a seller markets as “optimal”

Laboratory reference range< 15 µmol/L

Laboratory reference intervals

Under 8 µmol/LC< 8 µmol/L

B-vitamin and methylation supplement marketing, functional medicine

›View as table

Claim	Range	Source
Laboratory reference range	< 15 µmol/L	Laboratory reference intervals
Under 8 µmol/L	< 8 µmol/L	B-vitamin and methylation supplement marketing, functional medicine

Where the sources disagree

Homocysteine and HDL cholesterol are the two clearest examples in this registry of markers that predict risk but fail as targets. The intervention trials were run, they were large, and they were null. A supplement sold on the strength of lowering homocysteine is selling a change in a laboratory value that has not been shown to change what happens to you.

The marketed ranges, examined

Each claim gets its strongest possible case before it gets its criticism. Several of these are substantially correct.

Under 8 µmol/L

Promoted by b-vitamin and methylation supplement marketing, functional medicine

CConfounded

The strongest case for it

Elevated homocysteine is consistently associated with cardiovascular disease and cognitive decline across many observational cohorts.

What it leaves out

Trials that successfully lowered homocysteine with B vitamins did not reduce cardiovascular events. This is a textbook case of a marker that is associated with disease without being a useful lever, yet it anchors an entire category of methylation supplements.

Before you act on your result

Rises with impaired kidney function independent of B-vitamin status.
Sample handling matters; delayed processing falsely elevates results.
Lowering it with B vitamins has not reduced cardiovascular events in trials.

Last reviewed July 28, 2026How we grade evidence and attribute claims →

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HDL Cholesterol

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