Abstract: The present invention provides a method for screening the size of carrier for a subject in need, comprising: (a) providing a series of labeled carriers which have different sizes; (b) administering one of the series of carriers to a subject who suffers from an organ dysfunction; (c) monitoring biodistribution of the carrier of step (b) in said subject; (d) repeating steps (b) and (c) until all the series of carriers are administered and all the biodistribution of the series of carriers are monitored; and (e) determining the size of carrier for said subject in accordance with the retention time of the series of carriers in the dysfunctional organ of said subject. The method can be used as a screening platform for drug carrier, in which the optimal size of carrier can be screened for the dysfunctional organ of the subject.