DiaSys β-Hydroxybutyrate Standard is an aqueous standard for use in tests for quantitative in vitro determination of β-Hydroxybutyrate. For veterinary or research use only. The standard is used to calibrate β-Hydroxybutyrate assays. DiaSys β-Hydroxybutyrate Standard, both opened and unopened, must be stored refrigerated. Avoid contamination and protect from light. Once opened, DiaSys β-Hydroxybutyrate Standard is stable for 24 months if kept refrigerated and recapped immediatley after use.