OBJECTIVES: To qualitatively examine issues regarding unintentional dosing irregularities due to memory issues which may impact insulin taking behavior in people with diabetes. METHODS: Seven focus groups and eight individual interviews were held (Canada, Germany, China).  Respondents were recruited who had experienced at least two instances in the previous three months of forgetting the insulin dose, time/amount taken, or being unsure if they took their insulin. Transcripts were coded thematically, based on grounded theoretical approach. RESULTS: Sixty-four people participated: mean age 50.1 (range 18 to 72), (34% type 1, 66% type 2).  Analysis generated 6 domains: behaviors forgotten, reasons for forgetting, how they became aware that they had forgotten their insulin, consequences of forgetting, corrective actions, and the emotional impact of forgetting insulin. Respondents reported forgetting both bolus and basal insulin doses and often felt uncertain about if they administered their insulin dose, the dose amount or time taken.  Major reasons for these memory issues were: forgetting due to disruptions in their daily routine, distraction by social events, minor interruptions, and being generally busy. They became aware they forgot due to their own reminder systems as well as symptoms of hyperglycemia and blood glucose testing. People employ a wide variety of strategies and corrective actions when they think they have forgotten and often monitor their blood glucose more frequently following dosing irregularities.  Further, patients often question as to whether or not they took their insulin with greater frequency than times when they actually forgot and worry about the impact of these behaviors on maintaining stable blood glucose control.  CONCLUSIONS: Unintentional memory issues does impact insulin taking behavior , leads to dosing irregularities and contributes to patient uncertainty and worry about their diabetes management. Insulin strategies that assist patients in managing memory related dosing issues may reduce treatment costs, improve adherence and treatment outcomes.