Individuals with long-standing type 1 diabetes (T1D) are at increased risk of severe hypoglycemia secondary to impairments in normal glucose counterregulatory responses (CRR). Strategies to prevent hypoglycemia are often ineffective highlighting the need for novel therapies. ATP-sensitive potassium (KATP) channels within the hypothalamus are thought to be integral to hypoglycemia detection and initiation of CRRs, however, to date this has not been confirmed in human subjects. In this study, we examined whether the KATP-channel activator Diazoxide was able to amplify the CRR to hypoglycemia in T1D subjects with long-duration diabetes. A randomized, double-blind, placebo-controlled cross-over trial using a stepped hyperinsulinemic hypoglycemia clamp was performed in 12 T1D subjects with prior ingestion of Diazoxide (7mg/kg) or placebo. Diazoxide resulted in 37% increase in plasma levels of epinephrine and a 44% increase in plasma norepinephrine during hypoglycemia compared with placebo. In addition, a subgroup analysis revealed that participants with E23K polymorphism in the KATP channel had a blunted response to oral diazoxide. This study has therefore shown for the first time the potential utility of KATP channel activators to improve counterregulatory responses to hypoglycemia in individuals with T1D, and moreover that it may be possible to stratify therapeutic approaches by genotype.