OBJECTIVES: To identify real-world incidence and related costs of hypoglycemia among T2DM patients initiating insulin glargine (GLA). METHODS: Patient-level data from 6 published observational retrospective studies using health plan claim databases were pooled. Included were T2DM patients with continuous health plan coverage for 6 months before and 1 year after initiation, who were previously on oral antidiabetic drugs (OADs) or glucagon-like peptide-1 (GLP-1) analogs and initiated GLA (2007-2009) via disposable pen (GLA-P) or vial/syringe (GLA-V). In each study, observed differences between the two cohorts were removed by propensity score matching. Hypoglycemia and associated health care costs were measured over a 1-year follow-up period. RESULTS: Included were 14,911 GLA-P patients and 8,187 GLA-V patients (age 54.1 years, 53.5% men, mean Charlson Comorbidity Index 0.55, # of OADs 2.45, A1C 9.34% where available). During follow-up, prevalence rates of any hypoglycemia and inpatient/emergency room (ER)-related hypoglycemia were low overall, particularly for GLA-P (5.49% vs 7.70% and 1.60% vs 3.26%; both P<0.0001). Incidence rates of any hypoglycemia and inpatient/ER-related hypoglycemia were 25.7 and 3.8 events/100 patient years, and lower for GLA-P (any: 20.4 vs 35.5 events/100 patient years; ER-related: 2.6 vs 6.1 events/100 patient years; both P<0.0001). Hypoglycemia-related costs were lower for GLA-P ($225 vs $417; P=0.001). Hypoglycemia-related costs contributed 0.75% of overall health care costs and 1.5% of diabetes-related health care costs across both cohorts; in the GLA-P cohort the contribution was 0.55% and 1.07% (both P<0.001) of overall and diabetes-related costs, respectively. A1C reduction from baseline (N=1,896) was larger for GLA-P (−1.22% vs −0.86%, P=0.0012), and correlated with higher incidence of hypoglycemia (r=−0.151; P<0.0001). CONCLUSIONS: Patients initiating insulin glargine treatment showed low rates of hypoglycemia, especially when using a disposable pen device. Hypoglycemia-related costs were low, contributing a very small proportion to overall and diabetes-related health care costs.