3-Hydroxybutanal Lactaldehyde is an intermediate in the methylglyoxal metabolic pathway.

Methylglyoxal is converted to D-lactaldehyde by glycerol dehydrogenase (gldA).

Lactaldehyde is then oxidized to lactic acid by aldehyde dehydrogenase.

The molecule is chiral, its stereocenter being located on the second carbon atom.

In crystal form, three conformers occur as hemiacetal dimers with a 1,4-dioxane ring skeleton: In equilibrium solution, negligibly small amounts of the monomer and at least one five-membered ring dimer exist.