Beta-hydroxybutyrate compositions include a mixture of optically pure S-beta-hydroxybutyrate salts and acid(s) or non-racemic mixture of beta-hydroxybutyrate salts and acid(s) enriched with the S-enantiomer. The S-beta-hydroxybutyrate enantiomer modulates the effect of ketone bodies in the subject and controls the rate at which ketosis is achieved. Beta-hydroxybutyric acid is more rapidly absorbed and utilized by the body than salts or esters, enhances taste, and reduces the need to include citric acid or other edible acids. Beta-hydroxybutyrate salts are more slowly absorbed and utilized by the body and can provide one or more electrolytes. Compositions for controlling ketone body level in a subject may contain a dietetically or pharmaceutically acceptable carrier and optically pure S-beta-hydroxybutyrate or non-racemic mixture enriched with S-beta-hydroxybutyrate, wherein the compositions contain greater than 50% up to 100% by enantiomeric equivalents of S-beta-hydroxybutyrate and less than 50% down to 0% by enantiomeric equivalents of R-beta-hydroxybutyrate.