A retractable needle assembly for fluid collection, comprising: a housing comprising: a proximal end and a distal end; a sidewall having a longitudinal groove defined within a portion of the sidewall; a hollow bore extending between the proximal end and the distal end of the housing; an elongate plunger having a proximal end and a distal end, the distal end of the plunger defining a reservoir within the hollow bore for containing a fluid therein, the plunger adapted for slideable movement within the hollow bore, wherein movement of the plunger away from the distal end of the housing extracts the fluid into the reservoir and movement of the plunger towards the distal end of the housing expels the fluid from the reservoir; a hub disposed at least partially within the hollow bore, wherein a cannula is connected to a portion of the hub; a stopper connected to the distal end of the elongate plunger and slidably advanceable within the hollow bore to form a substantially fluid-tight seal with the hollow bore, the stopper disposed within the hollow bore at a location distal to the hub; and a needle retraction member engaged with the hub for manually selectable advancement of the cannula with respect to a portion of the housing, wherein the needle retraction member is movable along a longitudinal axis from an initial position in which at least a portion of the cannula is disposed outside the housing, to a retracted position in which the cannula is fully surrounded by the housing, and wherein the elongate plunger is movable about at least a portion of the hub for extracting the fluid into the reservoir or expelling the fluid from the reservoir, and wherein with the needle retraction member transitioned to the retracted position, the hub and the needle cannula remain stationary within the bore of the housing during movement of the plunger. a housing comprising: a proximal end and a distal end; a sidewall having a longitudinal groove defined within a portion of the sidewall; a hollow bore extending between the proximal end and the distal end of the housing; a proximal end and a distal end; a sidewall having a longitudinal groove defined within a portion of the sidewall; a hollow bore extending between the proximal end and the distal end of the housing; an elongate plunger having a proximal end and a distal end, the distal end of the plunger defining a reservoir within the hollow bore for containing a fluid therein, the plunger adapted for slideable movement within the hollow bore, wherein movement of the plunger away from the distal end of the housing extracts the fluid into the reservoir and movement of the plunger towards the distal end of the housing expels the fluid from the reservoir; a hub disposed at least partially within the hollow bore, wherein a cannula is connected to a portion of the hub; a stopper connected to the distal end of the elongate plunger and slidably advanceable within the hollow bore to form a substantially fluid-tight seal with the hollow bore, the stopper disposed within the hollow bore at a location distal to the hub; and a needle retraction member engaged with the hub for manually selectable advancement of the cannula with respect to a portion of the housing, wherein the needle retraction member is movable along a longitudinal axis from an initial position in which at least a portion of the cannula is disposed outside the housing, to a retracted position in which the cannula is fully surrounded by the housing, and wherein the elongate plunger is movable about at least a portion of the hub for extracting the fluid into the reservoir or expelling the fluid from the reservoir, and wherein with the needle retraction member transitioned to the retracted position, the hub and the needle cannula remain stationary within the bore of the housing during movement of the plunger.