The use of disease or multi-use models (i.e. one model that can be used to determine the cost effectiveness of many new technologies in a certain disease) is increasingly being advocated. Diabetes is a disease area where such models are relatively common; examples are the CORE Diabetes Model, which was used for National Institute for Health and Care Excellence (NICE) Guideline NG28, and the UK Prospective Diabetes Study (UKPDS) model. Recently, Eli Lilly has submitted a new diabetes model, the PRIME Type 2 Diabetes Model (PRIME T2D), to the NICE. This model was used in the NICE single technology appraisal (STA) process of tirzepatide (tradename Mounjaro®; Technology Appraisal 924). In this commentary we set out the key learnings from the External Assessment Group (EAG) perspective regarding this TA, the assessment of a disease model, and associated challenges.