The present disclosure relates to a capsule for preparing a solution for use with a measuring device for determining a measurand that depends on a concentration of at least one analyte in a sample. The capsule includes a wall completely enclosing an interior, at least one substance accommodated within the interior, and at least one stirring body. The present disclosure also relates to a system, which includes at least one capsule and a liquid container closed in a liquid-tight manner, which contains a predetermined volume of a liquid containing a solvent. In addition, the wall of the capsule is formed from a material which dissolves at least partially in the solvent.