OBJECTIVES: To compare units per day per claim (units) and costs per day per claim (costs) of comparable insulin products by Eli Lilly and Company (LLY) and Novo Nordisk (NN), adjusting for baseline patient differences, in state Medicaid claims data. METHODS: Claims for comparable LLY or NN insulin for patients with continuous coverage for ≥6 months before their first observed insulin claim (baseline) were identified from Missouri (MO: 1/1/2011-3/31/2012) and New Jersey (NJ: 1/1/2011-3/31/2013) de-identified Medicaid claims data. Units were calculated by multiplying total quantity per claim (in mL) by strength (1 mL=100 units) and dividing by total days supplied. Costs were calculated (for patients aged <65 years only, because drug costs for those aged ≥65 years are often covered by Medicare rather than Medicaid) by dividing the cost of a claim to insurers by total days supplied. Regression-adjusted units and costs were estimated using generalized estimating equation models, accounting for baseline demographics, select comorbidities, and antidiabetic medication use.  RESULTS: Claims for