Switching from oral antidiabetics to insulin injection is perceived as a major barrier by diabetes mellitus type-2 patients with fear for injection of insulin, but little is known about the extent. OBJECTIVE: To estimate the rate of starting insulin in newly identified diabetes mellitus patients, in patients starting with a combination of two oral antidiabetics and in patients with uncontrolled HBA1c levels while taking two oral antidiabetic agents. METHODS: A retrospective cohort study was conducted in the IPCI general practice database during the period 1996-2004. Patients with diabetes mellitus type II (DM-2) were classified as prevalent if DM-2 was diagnosed prior to entry in follow-up and as incident if diagnosed during follow-up. Three cohorts were identified to assess the rate and risk of starting insulin. Cohort A: all incident DM-2 patients, cohort B: all patients newly starting with a multiple pill oral combination therapy. Cohort C was a subset of B and comprised all patients on oral combination therapy who had uncontrolled HBA1c levels after at least 3 months of treatment. RESULTS: The source population comprised 5693 incident and 7456 prevalent DM-2 patients. In incident DM-2 patients 80% was treated pharmacologically within one year, 3% received an insulin based regimen as initial treatment, 76% started on a single oral antidiabetic. The rate of starting insulin was 0.6/100 PY in patients of cohort A, who started on oral treatment. The rate of starting insulin was 6.6/100 PY for patients in cohort B (n=1858). The one-year risk of starting insulin in cohort C (n=1167) was 3.8% (2.1-5.5%) for patients with HBA1c between 7-8% and 14.3% for patients with HBA1c above 8% at cohort entry. CONCLUSION: The rates and one-year risks of starting insulin are low even in DM-2 patients who remain uncontrolled after at least three months of oral combination therapy.