Abstract Objective To assess blood glucose in patients with uncontrolled type 2 diabetes mellitus treated with oral antidiabetic drugs in primary care at the time of referral to specialized endocrinologists, and the degree of implementation of the national consensus guidelines of the Spanish Society of Diabetes by evaluating steps one (S1), two (S2), and three (S3) of the escalating therapy. Material and methods Retrospective, observational study where 81 endocrinologists evaluated patients ≥40 years of age referred from primary care between July 2012 and July 2013, treated with 1 to 2 oral antidiabetic drugs but no insulin therapy, and with glycosylated hemoglobin (HbA1c) levels ≥6.5%. Patients also had to have HbA1c levels and both fasting and postprandial plasma glucose measurements from the previous three months. Results A total of 285 patients (57.6% males) were assessed. Mean (SD) age was 63.1 (9.7) years, mean HbA1c was 8.5 (1.2) %, mean FPG was 171.7 (43) mg/dL, and mean postprandial plasma glucose was 206.8 (50) mg/dL. In primary care, 26.0% of patients were at S1 and 74.0% were at S2. After referral to the endocrinologist, 9.8% of patients moved onto S1, 42.8% onto S2, and 47.4% onto S3. Oral antidiabetic drugs most commonly prescribed in primary care were metformin (90.2%), DPP-4 inhibitors (34.4%), and sulfonylureas (30.5%), while drugs most commonly used in the specialized endocrinology setting were metformin (86%), insulin (56.8%), and DPP-4 inhibitors (49.8%). The most commonly followed guidelines were those of the American Diabetes Association and the consensus guidelines of the Spanish Society of Diabetes, in 77% and 45% of cases respectively. Conclusions Approximately half the patients treated with oral antidiabetic drugs in primary care are prescribed insulin after referral to an endocrinology specialist. The most commonly followed guidelines in specialized care are the American Diabetes Association guidelines.