Deterioration of diabetes control can be the first harbinger of pancreatic cancer. However, little is known about how to distinguish patients with pancreatic cancer-related diabetes deterioration from those with type 2 diabetes progression. We aimed to characterize the glycated hemoglobin (HbA; 1c; ) and body weight profile of pancreatic cancer patients with deteriorating diabetes before the cancer diagnosis.; Using data from the UK-based Clinical Practice Research Datalink (CPRD) GOLD, we established a study population including pancreatic cancer patients with diabetes deterioration in the >0.5-3 years before the cancer diagnosis and non-cancer patients with deterioration of type 2 diabetes (comparison group). Patients were considered to have diabetes deterioration if their glucose-lowering treatment was intensified. We characterized the longitudinal trajectories of HbA; 1c; and body weight in pancreatic cancer patients compared with non-cancer patients before and after treatment intensification.; The mean absolute increase in HbA; 1c; from the pre-deterioration period, i.e. the time >1-2 years before treatment intensification, to the time of treatment intensification, was 1.5% ± 1.6% in pancreatic cancer patients vs. 0.9% ± 1.4% in non-cancer patients. After treatment intensification, mean HbA; 1c; remained elevated in pancreatic cancer patients, while it returned to the pre-deterioration level in non-cancer patients. Body weight decreased by 1.9% ± 6.4% in cancer patients and increased by 0.3% ± 5.2% in non-cancer patients between the pre-deterioration period and treatment intensification, on average.; Pancreatic cancer-related diabetes deterioration may frequently be characterized by pronounced increases in HbA; 1c; , persistent elevation of HbA; 1c; after treatment intensification, and concomitant weight loss.