Hypoglycemia, or low blood glucose, is the most common complication experienced by Type 1 diabetes mellitus (T1DM) patients. It is dangerous and can result in unconsciousness, seizures and even death. The most common physiological parameter to be e®ected from hypoglycemic reaction are heart rate (HR) and correct QT interval (QTc) of the electrocardiogram (ECG) signal. Based on physiological parameters, a genetic algorithm based fuzzy reasoning model is developed to recognize the presence of hypoglycemia. To optimize the parameters of the fuzzy model in the membership functions and fuzzy rules, a genetic algorithm is used. A validation strategy based adjustable¯tness is introduced in order to prevent the phenomenon of overtraining (over¯tting). For this study, 15 children with 569 sampling data points with Type 1 diabetes volunteered for an overnight study. The e®ectiveness of the proposed algorithm is found to be satisfactory by giving better sensitivity and speci¯city compared with other existing methods for hypoglycemia detection.