A system comprising: an insulin delivery device configured to deliver insulin to a user of the system; and a computer-based control unit associated with the insulin delivery device, the computer-based control unit having a user interface and a computer-based processor; wherein the computer-based processor is configured to calculate a relative insulin on board value (502; 602) of automated delivery (IOB_automated) by computing insulin on board for both the automated delivery (IOB_automated) and for the reference delivery over the same time period (IOB_reference) and then taking the difference (IOB_automated - IOB_reference) to find the relative insulin on board value (relative-IOB) to assign to the period of the automated delivery, wherein the reference delivery schedule is a basal rate of insulin that seeks to maintain static blood glucose levels; characterized in that the computer-based control unit is configured to display a function of the relative insulin on board value (502; 602) as it is calculated to vary over a time period, at least a portion of the time period being a future time, and to calculate and display a predicted change in glucose levels (506; 606) based on the function of the relative insulin on board value, wherein the future glucose level projections are created by calculating the projected change in insulin on board at each future time period, and then by multiplying the change by the user's sensitivity factor, the sensitivity factor being the amount that a user's blood glucose level decreases when dosed with 1 unit of insulin. an insulin delivery device configured to deliver insulin to a user of the system; and a computer-based control unit associated with the insulin delivery device, the computer-based control unit having a user interface and a computer-based processor; wherein the computer-based processor is configured to calculate a relative insulin on board value (502; 602) of automated delivery (IOB_automated) by computing insulin on board for both the automated delivery (IOB_automated) and for the reference delivery over the same time period (IOB_reference) and then taking the difference (IOB_automated - IOB_reference) to find the relative insulin on board value (relative-IOB) to assign to the period of the automated delivery, wherein the reference delivery schedule is a basal rate of insulin that seeks to maintain static blood glucose levels; by computing insulin on board for both the automated delivery (IOB_automated) and for the reference delivery over the same time period (IOB_reference) and then taking the difference (IOB_automated - IOB_reference) to find the relative insulin on board value (relative-IOB) to assign to the period of the automated delivery, wherein the reference delivery schedule is a basal rate of insulin that seeks to maintain static blood glucose levels; characterized in that the computer-based control unit is configured to display a function of the relative insulin on board value (502; 602) as it is calculated to vary over a time period, at least a portion of the time period being a future time, and to calculate and display a predicted change in glucose levels (506; 606) based on the function of the relative insulin on board value, wherein the future glucose level projections are created by calculating the projected change in insulin on board at each future time period, and then by multiplying the change by the user's sensitivity factor, the sensitivity factor being the amount that a user's blood glucose level decreases when dosed with 1 unit of insulin. to display a function of the relative insulin on board value (502; 602) as it is calculated to vary over a time period, at least a portion of the time period being a future time, and to calculate and display a predicted change in glucose levels (506; 606) based on the function of the relative insulin on board value, wherein the future glucose level projections are created by calculating the projected change in insulin on board at each future time period, and then by multiplying the change by the user's sensitivity factor, the sensitivity factor being the amount that a user's blood glucose level decreases when dosed with 1 unit of insulin.