The low relative charge-to-mass ratio offset of 4He2+ and 12C6+ enables simultaneous acceleration in hadron therapy accelerators. At the same energy per nucleon, helium ions exhibit a stopping range approximately three times greater than carbon ions. In the future, mixed helium and carbon ion beams could be exploited for online range verification during clinical treatment. One possibility for creating this mixed beam is accelerating 4He2+ and 12C6+ sequentially through the LINAC and subsequently "mixing" the ion species at injection energy in the synchrotron with a double injection scheme. In this talk, the sequential multi-turn injection of 4He2+ and 12C6+ at the MedAustron accelerator facility is presented. The implementation at the MedAustron synchrotron is discussed and challenges as well as potential solutions are highlighted. First experimental results showcasing the potential of the double injection scheme are presented and discussed.