A wearable medication infusion system, comprising: an infusion set comprising an insertion cannula; the infusion set connected by tubing to a wearable infusion pump, said pump comprising a housing having an on-board display, and within said housing a medication reservoir in fluid communication with the cannula; an actuator operatively communicating with the reservoir; a power source; and a microprocessor operatively communicating with the power source, the on-board display, the insertion cannula and the actuator; said infusion pump further comprising a program key insert aperture in the housing; a program key (119, 120, 121, 122, 123) received in the program key insert aperture; and a printed circuit board having one or more contacts closed by the program key inserted in the program key insert aperture, operatively communicating with the microprocessor to set a dosage rate for the infusion pump, further characterized in that a bottom side of the housing is sealed around the key insert aperture by a flexible elastomeric material to enable a water and leak proof pump, wherein the flexible elastomeric material has a sufficient flexibility to allow the program key (119, 120, 121, 122, 123) to access the contacts on the printed circuit board and securely seal the program key (119, 120, 121, 122, 123) against the key insert aperture; and the microprocessor unit is programmed to deliver a different dosage depending upon how many contacts are closed when the program key (119, 120, 121, 122, 123) is inserted, wherein the contacts of the program key (119, 120, 121, 122, 123) are extensions at different clock-hand positions extending radially from the perimeter of the program key (119, 120, 121, 122, 123). an infusion set comprising an insertion cannula; the infusion set connected by tubing to a wearable infusion pump, said pump comprising a housing having an on-board display, and within said housing a medication reservoir in fluid communication with the cannula; an actuator operatively communicating with the reservoir; a power source; and a microprocessor operatively communicating with the power source, the on-board display, the insertion cannula and the actuator; a medication reservoir in fluid communication with the cannula; an actuator operatively communicating with the reservoir; a power source; and a microprocessor operatively communicating with the power source, the on-board display, the insertion cannula and the actuator; said infusion pump further comprising a program key insert aperture in the housing; a program key (119, 120, 121, 122, 123) received in the program key insert aperture; and a printed circuit board having one or more contacts closed by the program key inserted in the program key insert aperture, operatively communicating with the microprocessor to set a dosage rate for the infusion pump, further characterized in that a bottom side of the housing is sealed around the key insert aperture by a flexible elastomeric material to enable a water and leak proof pump, wherein the flexible elastomeric material has a sufficient flexibility to allow the program key (119, 120, 121, 122, 123) to access the contacts on the printed circuit board and securely seal the program key (119, 120, 121, 122, 123) against the key insert aperture; a program key insert aperture in the housing; a program key (119, 120, 121, 122, 123) received in the program key insert aperture; and a printed circuit board having one or more contacts closed by the program key inserted in the program key insert aperture, operatively communicating with the microprocessor to set a dosage rate for the infusion pump, further characterized in that a bottom side of the housing is sealed around the key insert aperture by a flexible elastomeric material to enable a water and leak proof pump, wherein the flexible elastomeric material has a sufficient flexibility to allow the program key (119, 120, 121, 122, 123) to access the contacts on the printed circuit board and securely seal the program key (119, 120, 121, 122, 123) against the key insert aperture; and the microprocessor unit is programmed to deliver a different dosage depending upon how many contacts are closed when the program key (119, 120, 121, 122, 123) is inserted, wherein the contacts of the program key (119, 120, 121, 122, 123) are extensions at different clock-hand positions extending radially from the perimeter of the program key (119, 120, 121, 122, 123).