Romiset 250 mcg Injection Romiset 250 mcg is a prescription injectable medicine containing romiplostim. It helps the body produce more platelets by stimulating platelet-forming cells in the bone marrow. It is primarily used in chronic immune thrombocytopenia (ITP) when platelet levels remain low despite previous treatments. By increasing platelet production, it can help maintain platelet counts at a safer level and lower the risk of bleeding.