Abstract: In a method of determining insulin sensitivity in a patient, glucose level is sensed continuously. A first area under the curve representing the glucose level over time is calculated. An amount of insulin that has been administered to the patient is sensed. An estimation of insulin on board the patient is calculated based on the glucose level and the amount of insulin administered to the patient. A second area under the curve representing the insulin on board over time is calculated. Patient data indicative of at least one patient physical parameter is received. Information indicative of amount of glucose ingested by the patient during a meal is received. An insulin sensitivity output indicative of ability of insulin to stimulate glucose utilization and inhibit glucose production in the patient based on the first and second area under the curve, the patient data and the meal information is generated.