Macromolecular nanostructures that are used as drug carriers are characterized by their loading and release kinetics. Release studies commonly employ the dialysis method, in which a cellulose membrane separates the solution of released drug from the nanocarrier solution. We demonstrate that it is necessary to take the effect of the dialysis membrane on the release kinetics into account. Using a two-step approach, consisting of a calibration experiment of drug diffusion through the dialysis membrane in the absence of nanocarriers, and an experiment in the presence of nanocarriers, we are able to determine all kinetic rates and in particular to disentangle kinetic dialysis membrane properties from kinetic nanocarrier properties. We apply our general approach to experimental dexamethasone release data from core-multishell nanocarriers and demonstrate that our method yields a consistent description of the nanocarrier release kinetics.