An oily formulation of fulvestrant or derivatives thereof and a method for producing the same. The oily formulation comprises: fulvestrant or derivatives thereof in an amount of 10 mg/ml to 170 mg/ml; a lactate compound in an amount of 5 to 80% of the total weight of the formulation; a vegetable oil or synthetic oil (ester); an analgesic; and an optional antioxidant.