What is Homocysteine?

Homocysteine has two disposal routes. Folate, vitamin B12 and vitamin B6 are used to break it down or recycle it, and the kidneys clear what remains. It builds up when those vitamin pathways are working inefficiently, and it builds up when the kidneys are filtering less.

Each disposal route has a marker of its own. Active B12 shows how much of that vitamin is available for the breakdown pathway, and eGFR shows how much filtering capacity the kidneys have. Read with homocysteine, they say which route is behind a rise: a shortage of the vitamins on one side, reduced filtering on the other.

The supply of folate, B12 and B6 depends on what is eaten and on how well the gut absorbs it. Inherited variation matters too: the enzymes carrying out those routes differ between people, and a slower version leaves homocysteine sitting higher on the same vitamin intake.

Homocysteine follows B-vitamin intake and stores over weeks, and drifts more slowly, over months to years, as kidney function changes. Measuring about every four months keeps pace with the vitamin side; the kidney drift is slower than any one gap between readings and shows only across several of them. This is Do Health's monitoring schedule, not a general recommendation for everyone.