ChEBI: 3-hydroxyoctanoic acid is an 8-carbon, beta-hydroxy fatty acid which may be a marker for primary defects of beta-hydroxy fatty acid metabolism. Repeating unit of poly(3-hydroxyoctanoic acid), a biopolymer used by numerous bacterial species as carbon and energy reserves. It is a 3-hydroxy monocarboxylic acid, a 3-hydroxy fatty acid and a medium-chain fatty acid. It is functionally related to an octanoic acid. It is a conjugate acid of a 3-hydroxyoctanoate.