Type 3c diabetes mellitus (T3cDM), also known as pancreatogenic diabetes, refers to diabetes caused by disease of the exocrine pancreas. T3cDM is not commonly recognised by clinicians and frequently it is misclassified as T1DM, or more commonly, T2DM. T3cDM can be difficult to distinguish from T1DM and T2DM, and it often co-exists with the latter. The aim of this review is to describe T3cDM, along with its complications, diagnosis and management. We focus on the nutritional implications of T3cDM for those with chronic pancreatitis, and provide a practical guide to the nutritional management of this condition.