3-Hydroxy hexanoic acid, a hydroxylated fatty acid, is present in methyl-branched poly(3-hydroxyalkanoate) (PHA) polymers synthesized by P. oleovorans, P. putida, and D. tsuruhatensis. Additionally, it appears in the urine and serum of diabetic patients experiencing ketoacidosis, unlike in healthy individuals or diabetics without ketoacidosis. [Matreya, LLC. Catalog No. 1747]