An organoleptically acceptable composition containing a ketone body or a ketone body precursor including a hydroxybutyrate ester and a flavouring is provided and gives improved palatability and user adherence to the intended dose regime. The flavouring may be a bitter flavouring and the composition may further contain an adsorbent for the ketone such that on ingestion, the bitterness of the composition may be masked. The composition may be in the form of a solid, gel or liquid and provides increased blood ketone levels and may be used in therapy or in treating muscle impairment or fatigue.