BACKGROUND: Hypoglycemia varies between patients with type 1 diabetes and is the main obstacle to therapy intensification. We investigated known and potential risk factors for hypoglycemia in subjects with type 1 diabetes. METHOD: In the ASPIRE In-Home study (NCT01497938), a randomized trial of the threshold suspend (TS) feature of sensor-augmented insulin pump (SAP) therapy, subjects' propensity to nocturnal hypoglycemia (NH) was established in a 2-week run-in phase and assessed in a 3-month study phase via continuous glucose monitoring. Categorical variables were tested for association with NH rates in both phases. RESULTS: Elevated rates of NH were significantly associated with baseline A1C =7%, with bolus insulin deliveries unassisted by the bolus estimation calculator, and with assignment to the control group during the study phase. CONCLUSIONS: Routine use of the TS feature and the bolus estimation calculator are strategies that may reduce the risk of NH.