OBJECTIVE: The study explores whether type 2 diabetes (T2D) diagnosis affects food consumption patterns in line with the dietary recommendations provided to individuals in relation to a diagnosis. DESIGN: Based on detailed food purchase data, we explore which dietary changes are most common following a T2D diagnosis. Changes are investigated for several energy-adjusted nutrients and food groups and overall adherence to dietary guidelines. SETTING: We use data on diagnosis of T2D and hospitalisation in relation to T2D for a sample of adult Danes registered in the official patient register. This is combined with detailed scanner data on food purchases, which are used as a proxy for dietary intake. PARTICIPANTS: We included 274 individuals in Denmark who are diagnosed during their participation in a consumer panel where they report their food purchases and 16 395 individuals who are not diagnosed. RESULTS: Results suggest some changes in dietary composition following diagnosis, as measured by a Healthy Eating Index and for specific food groups and nutrients, although the long-term effects are limited. Socio-economic characteristics are poor predictors of dietary changes following diagnosis. Change in diet following diagnosis vary with the pre-diagnosis consumption patterns, where individuals with relatively unhealthy overall diets prior to diagnosis improve overall healthiness more compared to individuals with relatively healthy diets prior to diagnosis. CONCLUSIONS: Adherence to dietary advice is low, on average, but there is large variation in behavioural change between the diagnosed individuals. Our results stress the difficulty for diagnosed individuals to shift dietary habits, particularly in the long term.