If it has already been reconstituted with AA, that isn't generally a good idea because you run the risk of degrading the IGF because of the reaction between the two chemicals--meaning the BA in the bacteriostatic water. It is best to reconstitute with one or the other. If you can handle the AA, then reconstitute your IGF with bacteriostatic water and use it immediately. AA is used because it buffers the IGF and keeps it good for a longer period of time whereas BS does not.