Models are presented to explain the physical conditions in the circumstellar envelope surrounding the red supergiant Alpha Orionis. The models of the CO density and neutral atomic potassium density are calculated for the outer shell to reproduce simultaneously both the radio detection of CO and optical measurements of the amount of scattering by neutral potassium around Alpha Ori. CO and potassium loss rates of 7 x 10 to the 39th/sec and 8 x 10 to the 37th/sec are obtained, which imply a potassium to carbon ratio greater than that of the sun by about a factor of 25. The low carbon abundance may be attributed to extensive CNO processing, and, together with the potassium abundance, indicates a total mass loss rate of 0.000015 solar masses/year. The mass loss, mass and abundance properties of Alpha Ori suggest it to be the progenitor of a Type II supernova such as Cas A.