OBJECTIVE Twenty-six states and the District of Columbia expanded Medicaid in January 2014 pursuant to the Affordable Care Act (ACA); 24 states did not. This created an opportunity to examine the impact of Medicaid expansion on the number of Medicaid patients with newly identified diabetes among enrollees (19–64 years of age) who had laboratory testing through Quest Diagnostics.

RESEARCH DESIGN AND METHODS Newly identified diabetes was defined as an ICD-9 diagnosis code of 250.x (diabetes) or hemoglobin A_1c of >6.4% (46 mmol/mol) within the first 6 months of a calendar year and the absence of both in the preceding calendar year within our data repository.

RESULTS We identified 215,398 and 218,890 patients who met our definition of newly diagnosed diabetes within the first 6 months of 2013 (control period) and 2014 (study period), respectively (a 1.6% increase). We identified 26,237 Medicaid-enrolled patients with new diabetes in the control period vs. 29,673 in the study period: an increase of 13%. The number of Medicaid-enrolled patients with newly identified diabetes increased by 23% (14,625 vs. 18,020 patients) in the 26 states (and District of Columbia) that expanded Medicaid compared with an increase of 0.4% (11,612 vs. 11,653 patients) in the 24 states that did not expand Medicaid during this period. Similar differences were observed in younger and older adults and for both men and women.

CONCLUSIONS This study suggests that in the states that expanded Medicaid under the ACA, an increased number of Medicaid patients with diabetes are being diagnosed and treated earlier. This could be anticipated to lead to better long-term outcomes.