Understanding 'Quantity Sufficient to Make' (QS) in Prescriptions

Quantity sufficient to make (QS or q.s.) is a direction given in a prescription for a compound medication. It indicates the desired final combined or total volume or quantity, typically of a final solution, suspension or mixture. The total quantity of the preparation is then attained by adding, as necessary, some or all of the solvent of choice, usually but not always water.

QS is an abbreviation for the Latin quantum sufficit, which means "sufficient quantity". It is not a precise measurement, and the amount of solvent that is added will depend on the desired concentration of the final product.