The invention relates to an adaptor (10) for coupling with a medical container (1) filled with a number N of doses of a product, comprising:- a gripping member (20) for securing the adaptor to the medical container, said gripping member including one needle access port (30) intended to face the outer surface of the septum of the medical container,- marking means (41, 42, 42a) coupled to said needle access port, for designating to a user a not yet pierced area of said outer surface, for completing the next of said N successive piercings. The invention also relates to an assembly comprising a medical container and such an adaptor.
