An injectable form of a polysaccharide isolated from the radix of Astragalus membranaceus (PG2), used in traditional Chinese medicine, with potential hematopoiesis inducing and immunomodulating activities. Upon injection, APS may be able to relieve certain chemotherapy-induced side effects, including myelosuppression, fatigue, mucositis, pain, nausea and vomiting, as well as loss of appetite and body weight. Also, APS may exert immunostimulatory activities by stimulating B-lymphocytes, activating T-lymphocytes, inducing cytokine production, and activating macrophages and natural killer cells through as of yet unidentified mechanism(s). APS may improve compliance of radiotherapy and/or chemotherapy.