[ Beta-hydroxybutyric acid, β-Hydroxybutyric acid, 3-hydroxybutyric acid, D-3-hydroxybutyrate ]
Although not a ketone itself, it is one of the three chemicals, or ketone bodies, produced during the metabolic state of ketosis or ketoacidosis. Beta-hydroxybutyric acid is the first of these to be produced in the fasting state.
Beta-hydroxybutyric acid levels increase with exercise, calorie restriction, fasting, and ketogenic diets. It is able to cross the blood-brain-barrier into the central nervous system.
The compound can be used as an energy source by the brain when blood glucose is low.