Holotranscobalamin (active B12)Nutrition library
LibraryBlood markersVitamins & minerals
Holotranscobalamin (active B12)
Holotranscobalamin (active B12) is the tissue-available fraction — often the earliest marker of functional B12 insufficiency.
Low holo-B12 with normal total B12 suggests early deficiency or transport issues. Particularly useful when homocysteine is elevated.
How to read it
Display-only in Trends but clinically valuable alongside serum B12 and homocysteine.
Trimester context
| Stage | For the mother | For the baby |
|---|---|---|
| First trimester | — | — |
| Second trimester | Functional B12 strain often appears as demands peak. | Supports methylation during rapid fetal growth. |
| Third trimester | — | — |