The initial structural investigations of glycolide were performed on the pure material itself using a liquid pressure-transmitting medium to ensure that the structural information could be extracted under hydrostatic or pseudo-hydrostatic conditions. These conditions are not typical in a tableting environment, hence we needed to demonstrate that the transition would still occur in the presence of excipients and under conditions of tableting. An initial test was performed on an in-house compaction simulator (HB50, Huxley Bertram Engineering Ltd) and using a terahertz time-domain spectroscopy (THz-TDS) system (TeraPulse Lx Spectrometer, TeraView Ltd). A formulation containing glycolide (20% wt.), microcrystalline cellulose (VIVAPUR® PH-112; 79% wt.) and magnesium stearate (1% wt.) was loaded into the compaction simulator before applying incremental load and characterizing tablets offline using the THz-TDS system. The resulting spectra enable the measurement of the absorption coefficient of the solids on increasing pressure hence it can be inferred that an observable discontinuous change can be attributed to a phase transformation in the material of study. There is a clear discontinuous change to the spectra on compression above 150 MPa even in the presence of the excipients (Figure ) warranting further investigation using XRD-CT.