Insulin detemir is a long-acting basal insulin analogue recently introduced in veterinary medicine for treatment of canine diabetes mellitus. As there are only limited studies in dogs, long-term evaluation of insulin detemir in veterinary medicine is required. In this study, we investigated trends in12-hour blood glucose concentration during hospitalization and evaluated initial and following doses of insulin detemir for several months in six diabetic dogs. The mean levels of blood glucose over 12-hour periods were between 113.5 to 327.2 mg/dL, and the average glucose nadir was 103 mg/dL in the six dogs. The dogs were treated with a mean dosage of 0.24 U/kg of insulin detemir, but hypoglycemia was observed in four of the dogs at the first monthly follow-up. Thus, insulin doses were adjusted according to the nadir levels of glucose observed during the follow-up periods (range, 1 to 16 months). The total range of insulin doses throughout the study period was between 0.1 and 0.4 U/kg. Changes in insulin doses in each dog during the follow-up period were not variable. We suggest that insulin detemir might be not only an alternative choice against traditional insulin for patients with insulin resistance or concurrent disease but also an effective home therapy medication in canine patients with DM. This study could help inform veterinary practitioners regarding the use of insulin detemir for canine insulin-dependent DM.