Aims: To study the time and costs of insulin treatment of newly registered outpatients with Type 2 diabetes mellitus (T2DM). Methods: In total, 355 patients with T2DM were registered on their first visit to one of 11 diabetes clinics across Japan. Of these, 313 were not being treated with insulin (the non-insulin group), whereas 42 were (the insulin group). In the insulin group, 26 were already on insulin at the first visit, whereas 16 were started on insulin after their first visit. The time and costs involved in the care were recorded over the following 5 months. Results: In the first 3 months, considerable time was expended in both groups, with the time spent by physicians a little (but significantly) longer for the insulin group. The total time expended by all care providers was approximately 1.3-fold greater for the insulin compared with the non-insulin group. The total cost and total cost/min for the insulin group was almost twice that for the non-insulin group. Over the 5-month period, mean HbA1c in the non-insulin group improved from 8.0% to 6.5%, with 72% achieving a glycemic target of HbA1c # 6.5%. In contrast, in the insulin group, mean HbA1c improved from 9.4% to 7.6%, with only 39% achieving the target. There were no reports of major hypoglycemic events in either group and body mass index remained stable. Conclusions: The insulin therapy for T2DM can be achieved safely and effectively at outpatient clinics, even though it requires considerably more time and resources than non-insulin therapy.