We have examined lyophilised BSA formulations (F1-F4) and lyophilised mAb formulations (F5-F7). By performing temperature variable THz-TDS experiments we studied the structural dynamic properties of these formulations. A monotonous increase of absorption coefficient with temperature was observed for F4, F5, and F6, while the absorption coefficient plateaus at high temperatures for F1, F2, F3, and F7. All the formulations examined exhibit three temperature regimes, with a distinct T g, and T g,↵ . We propose two hypotheses for the pathway protein molecules can proceed upon heating: (1) adopting different conformational states until reaching a confined state as demonstrated by a plateau in the THz-TDS data, or (2) the increase in temperature coupled with an increase in entropy leads to the protein molecules continuously exploring environments of high conformational energy and molecular mobility. Our work provides insight into the effects of excipients, including sucrose, trehalose, polysorbate 80, and arginine on the dynamics of formulations. Additionally, while the value of the transition temperatures does not change significantly between formulations, the value of the gradient does differs significantly and this is a parameter which can be obtained uniquely with THz-TDS, and could be indicative of the number of conformational environments explored by a protein system. Furthermore, we used FTIR and CD spectroscopy to investigate the structural changes of formulations and demonstrated that there is no change in the secondary structure following heating, however there is a decrease in -sheet content of the neat BSA as additives were incorporated in the formulations produced. Additional solid-state NMR measurements investigated changes of the formulations by 13 C CP-MAS. A spectral analysis of the formulations showed no major chemical structural changes of the protein structures after heating. NMR relaxation time measurements of T 1 and T 1⇢ revealed a homogeneous sugar and protein phases on length scales of 2 5 nm and 20 50 nm after lyophilisation. No changes in the phase mixing were observed after heating BSA formulations containing no or 0.04% polysorbate 80 as additive. F6 and F7 show T 1⇢ decrease after heating indicating a change of dynamics in the system. The addition of 0.04% polysorbate in F7 resulted a small phase separation on the 2 5 nm scale. This work provides a framework for understanding the dynamics of complex formulations and demonstrates that THz-TDS is an effective method to measure the molecular dynamics and temperature-dependant behaviour of solid-state formulations. Furthermore, the changes in protein and excipient interactions probed by THz-TDS in the dry state and may be linked to chemical stability. Specifically, systems which exhibit a plateau include proteins confined in a particular structure, which may result in exposure or protection or potential degradation sites, depending on the specific protein structure. Thus, such confined proteins may follow a different degradation pathway and/or kinetics to a non-confined protein which exhibits increasing absorption at terahertz frequencies. This relationship would provide a predictive metric for long-term chemical stability of the protein, however, additional work is required to explore these effects in detail.