Two cases are described of patients who present with severe malnutrition more than five years after undergoing a Roux-en-Y gastric bypass and who have deficiencies of both micronutrients (vitamins and minerals) and macronutrients (proteins). This problem appears to be caused by both iatrogenic malabsorption after gastric bypass as well as dysphagia due to a local anastomotic complication (stenosis and marginal ulcer). Although both the severity of the deficiencies and the timing are exceptional, we want to emphasize the importance of lifelong supplement use and follow-up after bariatric surgery. Given the important role of general practitioners in this, we argue for implementation of this topic in national guidelines to improve the quality of follow-up.