An automatic drug delivery device, comprising: a processor, a reservoir configured to contain a therapeutic exogenous substance; a pump mechanism communicatively coupled to the processor, and fluidically coupled to the reservoir; and a memory coupled to the processor and configured to store a substance delivery history and programming code that, when executed by the processor, cause the drug delivery device to: estimate an amount of the therapeutic exogenous substance to deliver to a user; determine an insulin adjustment factor utilizing an estimated relative therapeutic exogenous substance concentration, wherein the estimated relative therapeutic exogenous substance concentration is determined based on the sum of the past actual therapeutic exogenous substance deliveries over a number of delivery cycles versus the expected insulin needs for the user based on their total daily therapeutic exogenous substance amounts, accounting for the decay and/or absorption of the exogenous substance within the body over time; calculate a compensating dose of the therapeutic exogenous substance based on the estimated amount of the therapeutic exogenous substance to deliver that is adjusted by the insulin adjustment factor; and causing the calculated compensating dose of the therapeutic exogenous substance to be expelled from the reservoir by the pump mechanism. a processor, a reservoir configured to contain a therapeutic exogenous substance; a pump mechanism communicatively coupled to the processor, and fluidically coupled to the reservoir; and a memory coupled to the processor and configured to store a substance delivery history and programming code that, when executed by the processor, cause the drug delivery device to: estimate an amount of the therapeutic exogenous substance to deliver to a user; determine an insulin adjustment factor utilizing an estimated relative therapeutic exogenous substance concentration, wherein the estimated relative therapeutic exogenous substance concentration is determined based on the sum of the past actual therapeutic exogenous substance deliveries over a number of delivery cycles versus the expected insulin needs for the user based on their total daily therapeutic exogenous substance amounts, accounting for the decay and/or absorption of the exogenous substance within the body over time; calculate a compensating dose of the therapeutic exogenous substance based on the estimated amount of the therapeutic exogenous substance to deliver that is adjusted by the insulin adjustment factor; and causing the calculated compensating dose of the therapeutic exogenous substance to be expelled from the reservoir by the pump mechanism. estimate an amount of the therapeutic exogenous substance to deliver to a user; determine an insulin adjustment factor utilizing an estimated relative therapeutic exogenous substance concentration, wherein the estimated relative therapeutic exogenous substance concentration is determined based on the sum of the past actual therapeutic exogenous substance deliveries over a number of delivery cycles versus the expected insulin needs for the user based on their total daily therapeutic exogenous substance amounts, accounting for the decay and/or absorption of the exogenous substance within the body over time; calculate a compensating dose of the therapeutic exogenous substance based on the estimated amount of the therapeutic exogenous substance to deliver that is adjusted by the insulin adjustment factor; and causing the calculated compensating dose of the therapeutic exogenous substance to be expelled from the reservoir by the pump mechanism.