BACKGROUND: The obesity epidemic has been associated with a surge in diagnoses of diabetes and pre-diabetes in the general population, but a high proportion of individuals are unaware that they have these conditions, which confer higher vascular risk, yet are amenable to treatment. Given the adverse effects of hyperglycemia on post-stroke outcomes and recurrent vascular risk, we investigated the burden of undiagnosed diabetes and pre-diabetes among stroke survivors. METHODS: We assessed prevalence of undiagnosed diabetes and pre-diabetes (HbA1c ≥6.5% and HbA1c 5.7-6.4% without self-reported physician-diagnosis) among 1070 non-pregnant adult (≥20 years) stroke survivors who participated in the National Health and Nutrition Examination Surveys 1999-2010. Logistic regression was used to assess the relationship between race-ethnicity and odds of undiagnosed diabetes/prediabetes, adjusting for sociodemographic characteristics and medical comorbidities. RESULTS Among an estimated 5,102,279 adult stroke survivors in the US, 3.7% had undiagnosed diabetes, while 32.3% had undiagnosed pre-diabetes. Prevalence of undiagnosed diabetes was 7.5% in non-Hispanic blacks (NHBs), 4.4% in Hispanics, and 3.1% in non-Hispanic whites (NHWs). Prevalence of undiagnosed pre-diabetes was highest in NHBs (37.8%), followed by NHWs (31.6%) and Hispanics (26.3%). Compared to NHWs and Hispanics, NHB stroke survivors with undiagnosed diabetes/pre-diabetes were younger (mean age 59 years vs. 70 and 67 years), more likely to be on antihypertensive medications (73% vs. 66% and 58%), and more likely to smoke (30% vs. 22% and 11%). After multivariate analysis, NHBs were more likely to have undiagnosed diabetes/pre-diabetes than NHWs (OR 2.12, 95% CI 1.31-3.44; p=0.002). CONCLUSIONS: A high proportion (one in 3) of stroke survivors in the US has undiagnosed pre-diabetes and the highest rates of diabetes and pre-diabetes are seen among NHBs, even after adjusting for confounders. Systematic screening and treatment at the time of the index stroke may boost overall clinical outcomes and bridge these racial disparities.