A wearable infusion pump, comprising: a housing having an on-board display, and within said housing an insertion cannula; 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 (119, 120, 121, 122, 123) 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 (119, 120, 121, 122, 123) inserted in the program key insert aperture, operatively communicating with the microprocessor to set a dosage rate for the infusion pump; wherein the onboard display comprises separate light emitting diodes (111, 112, 113, 114, 115) or digitally generated alphanumeric characters indicating: (a) ON/OFF state; (b) fill state of the reservoir; (c) basal rate set status; and (d) error condition characterized in that the wearable infusion pump further comprises a user operable switch causing the insertion cannula to be inserted into a patient's subcutaneous tissue; 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) such that the dosage programmed by the key can be readily ascertained by the user looking at the key from its shape. a housing having an on-board display, and within said housing an insertion cannula; 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; an insertion cannula; 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 (119, 120, 121, 122, 123) insert aperture in the housing; a program key (119, 120, 121, 122, 123) received in the program key insert aperture; a program key (119, 120, 121, 122, 123) insert aperture in the housing; a program key (119, 120, 121, 122, 123) received in the program key insert aperture; the wearable infusion pump further comprises a user operable switch causing the insertion cannula to be inserted into a patient's subcutaneous tissue; 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) such that the dosage programmed by the key can be readily ascertained by the user looking at the key from its shape.