An adjustable dose drug delivery system comprising: a plunger, a syringe body, an inner housing, a plunger sleeve, an outer housing, and a rotating collar, wherein the plunger comprises a stopper at a distal end, a plunger flange comprising a center at a proximal end, and a plunger stem fixed to the center of the plunger flange at a proximal end; the syringe body comprises a syringe tip at a distal end and an open proximal end comprising a syringe body flange, wherein the plunger is slidably deposed by inserting the stopper into the open proximal end of the syringe body and pushing the plunger flange toward the syringe body distal end; the inner housing comprises a proximal end and a distal end and encloses the syringe body and is affixed thereto, wherein the inner housing further comprises a plurality of dosage stops spirally deposed between the inner housing proximal end and distal end; the plunger sleeve is distal to the plunger flange, and has a circumference within a plunger flange circumference and distal thereto, and encloses, and is external to, the plunger stem, and is deposed outside the inner housing and, when pushed toward the syringe body distal end, slides along the inner housing toward the plurality of dosage stops, wherein the plunger sleeve further comprises a closed slot running parallel to the plunger stem, and a dosage stop engagement mechanism that engages a dosage stop when the plunger sleeve slides along the inner housing, said engagement preventing (a) further sliding of the plunger sleeve along the inner housing and (b) further insertion of the plunger toward the syringe body distal end; the outer housing encompasses the inner housing and comprises a proximal end overlapping and deposed outside the plunger sleeve; and the rotating collar surrounds the plunger sleeve and the proximal end of the outer housing and is rotationally joined to the plunger sleeve by a pin inserted into the plunger sleeve closed slot, wherein the rotating collar further comprises a window displaying dosage information present on the outer housing, and rotating the rotating collar displays a series of specific dosages in the window and rotates the plunger sleeve to align the dosage stop engagement mechanism to a dosage stop on the inner housing corresponding to the specific dosage displayed in the window. a plunger, a syringe body, an inner housing, a plunger sleeve, an outer housing, and a rotating collar, wherein the plunger comprises a stopper at a distal end, a plunger flange comprising a center at a proximal end, and a plunger stem fixed to the center of the plunger flange at a proximal end; the syringe body comprises a syringe tip at a distal end and an open proximal end comprising a syringe body flange, wherein the plunger is slidably deposed by inserting the stopper into the open proximal end of the syringe body and pushing the plunger flange toward the syringe body distal end; the inner housing comprises a proximal end and a distal end and encloses the syringe body and is affixed thereto, wherein the inner housing further comprises a plurality of dosage stops spirally deposed between the inner housing proximal end and distal end; the plunger sleeve is distal to the plunger flange, and has a circumference within a plunger flange circumference and distal thereto, and encloses, and is external to, the plunger stem, and is deposed outside the inner housing and, when pushed toward the syringe body distal end, slides along the inner housing toward the plurality of dosage stops, wherein the plunger sleeve further comprises a closed slot running parallel to the plunger stem, and a dosage stop engagement mechanism that engages a dosage stop when the plunger sleeve slides along the inner housing, said engagement preventing (a) further sliding of the plunger sleeve along the inner housing and (b) further insertion of the plunger toward the syringe body distal end; a closed slot running parallel to the plunger stem, and a dosage stop engagement mechanism that engages a dosage stop when the plunger sleeve slides along the inner housing, said engagement preventing (a) further sliding of the plunger sleeve along the inner housing and (b) further insertion of the plunger toward the syringe body distal end; the outer housing encompasses the inner housing and comprises a proximal end overlapping and deposed outside the plunger sleeve; and the rotating collar surrounds the plunger sleeve and the proximal end of the outer housing and is rotationally joined to the plunger sleeve by a pin inserted into the plunger sleeve closed slot, wherein the rotating collar further comprises a window displaying dosage information present on the outer housing, and rotating the rotating collar displays a series of specific dosages in the window and rotates the plunger sleeve to align the dosage stop engagement mechanism to a dosage stop on the inner housing corresponding to the specific dosage displayed in the window. the rotating collar further comprises a window displaying dosage information present on the outer housing, and rotating the rotating collar displays a series of specific dosages in the window and rotates the plunger sleeve to align the dosage stop engagement mechanism to a dosage stop on the inner housing corresponding to the specific dosage displayed in the window.