A device for delivering a fluid medicament into or through the skin of a user, the device comprising: a reusable part having a generally T-shaped configuration including a leg portion, the leg portion having a first capacitor sensor and a second capacitor sensor coupled thereto, comprising: a drive component contained in the leg portion; and a control unit for controlling the drive component; and a disposable part engageable with the reusable part, the disposable part comprising: a first reservoir for containing the fluid medicament; a first plunger head moveable by a first lead screw in the first reservoir; a first nut having an inner threaded profile that engages with threads on the first lead screw and operable to cause linear translation of the first lead screw upon rotation of the first nut, wherein when the reusable part and the disposable part are attached, the first nut is operably coupled with and rotatable by the drive component in a direction controllable by the control unit; a second reservoir for containing additional fluid medicament; a second plunger head for driving the additional fluid medicament out of the second reservoir, the second plunger head moveable in the second reservoir by a second lead screw; and a second nut having an inner threaded profile that engages with threads on the second lead screw and operable to cause linear translation of the second lead screw upon rotation of the second nut, wherein when the reusable part and the disposable part are attached, the second nut is operably coupled with and rotatable by the drive component in a direction controllable by the control unit; and wherein the first capacitive sensor and the second capacitive sensor are respectively positioned opposite and/or facing the respective first and second reservoirs (106a, 106b) so as to provide an output related to a quantity of fluid stored in the first and second reservoirs (106a, 106b). a reusable part having a generally T-shaped configuration including a leg portion, the leg portion having a first capacitor sensor and a second capacitor sensor coupled thereto, comprising: a drive component contained in the leg portion; and a control unit for controlling the drive component; and a drive component contained in the leg portion; and a control unit for controlling the drive component; and a disposable part engageable with the reusable part, the disposable part comprising: a first reservoir for containing the fluid medicament; a first plunger head moveable by a first lead screw in the first reservoir; a first nut having an inner threaded profile that engages with threads on the first lead screw and operable to cause linear translation of the first lead screw upon rotation of the first nut, wherein when the reusable part and the disposable part are attached, the first nut is operably coupled with and rotatable by the drive component in a direction controllable by the control unit; a second reservoir for containing additional fluid medicament; a second plunger head for driving the additional fluid medicament out of the second reservoir, the second plunger head moveable in the second reservoir by a second lead screw; and a second nut having an inner threaded profile that engages with threads on the second lead screw and operable to cause linear translation of the second lead screw upon rotation of the second nut, wherein when the reusable part and the disposable part are attached, the second nut is operably coupled with and rotatable by the drive component in a direction controllable by the control unit; and wherein the first capacitive sensor and the second capacitive sensor are respectively positioned opposite and/or facing the respective first and second reservoirs (106a, 106b) so as to provide an output related to a quantity of fluid stored in the first and second reservoirs (106a, 106b). a first reservoir for containing the fluid medicament; a first plunger head moveable by a first lead screw in the first reservoir; a first nut having an inner threaded profile that engages with threads on the first lead screw and operable to cause linear translation of the first lead screw upon rotation of the first nut, wherein when the reusable part and the disposable part are attached, the first nut is operably coupled with and rotatable by the drive component in a direction controllable by the control unit; a second reservoir for containing additional fluid medicament; a second plunger head for driving the additional fluid medicament out of the second reservoir, the second plunger head moveable in the second reservoir by a second lead screw; and a second nut having an inner threaded profile that engages with threads on the second lead screw and operable to cause linear translation of the second lead screw upon rotation of the second nut, wherein when the reusable part and the disposable part are attached, the second nut is operably coupled with and rotatable by the drive component in a direction controllable by the control unit; and wherein the first capacitive sensor and the second capacitive sensor are respectively positioned opposite and/or facing the respective first and second reservoirs (106a, 106b) so as to provide an output related to a quantity of fluid stored in the first and second reservoirs (106a, 106b).