There is little information on sedimentation time of glass pieces in glass ampoules. In this study, we predicted the sedimentation time of glass pieces in commercial injections using Stokes equations. First, we measured the viscosity and density of 21 types of commercial injection. The viscosity of injections changed largely with temperature, and the higher viscosity showed a longer predicted sedimentation time. Moreover, considering factors such as storage temperature and the height from bottom to surface of injections, the predicted sedimentation times of glass pieces was long, that is 3.9-19.0 min/ampoule at 20°C. These results suggest the risk of mixing glass pieces in parts of commercial injections.