A syringe assembly (100, 200, 300) comprising: a fluid barrel (110, 210, 310) including a sidewall having an inside surface defining a fluid chamber for retaining fluid and having a first cross-sectional width, an open proximal end and a distal end including a distal wall; a plunger rod (160, 260, 360) disposed within the fluid chamber comprising a distal end, a proximal end, a plunger rod body extending from the distal end to the proximal end, and a stopper disposed at the distal end of the plunger rod for forming a fluid-tight seal with the inside surface of the barrel; a retraction barrel (120, 220, 320) disposed adjacent to the sidewall of the fluid barrel, the retraction barrel including a wall having an interior surface defining a needle chamber, an open proximal end, an open distal end including a barrier wall, an aperture (118, 218, 318) between the wall of the fluid barrel and the sidewall of the fluid barrel such that the fluid chamber and the needle chamber are in fluid communication and a needle hub assembly comprising a needle hub, a needle cannula attached to the needle hub in fluid communication with the aperture, the needle hub assembly biased to move in the proximal direction; a retraction mechanism to the needle cannula to retract into the retraction barrel; and a trigger element (190, 290, 390) characterized in that the retraction barrel is nested with the fluid barrel and the retraction barrel has cross-sectional dimension that is less than 90% of the cross-sectional dimension of the fluid barrel and the trigger element is moveable with the plunger rod and extending into the needle chamber of the retraction barrel, the trigger element providing a trigger force causing the needle cannula to retract into the retraction barrel. a fluid barrel (110, 210, 310) including a sidewall having an inside surface defining a fluid chamber for retaining fluid and having a first cross-sectional width, an open proximal end and a distal end including a distal wall; a plunger rod (160, 260, 360) disposed within the fluid chamber comprising a distal end, a proximal end, a plunger rod body extending from the distal end to the proximal end, and a stopper disposed at the distal end of the plunger rod for forming a fluid-tight seal with the inside surface of the barrel; a retraction barrel (120, 220, 320) disposed adjacent to the sidewall of the fluid barrel, the retraction barrel including a wall having an interior surface defining a needle chamber, an open proximal end, an open distal end including a barrier wall, an aperture (118, 218, 318) between the wall of the fluid barrel and the sidewall of the fluid barrel such that the fluid chamber and the needle chamber are in fluid communication and a needle hub assembly comprising a needle hub, a needle cannula attached to the needle hub in fluid communication with the aperture, the needle hub assembly biased to move in the proximal direction; a retraction mechanism to the needle cannula to retract into the retraction barrel; and a trigger element (190, 290, 390) characterized in that the retraction barrel is nested with the fluid barrel and the retraction barrel has cross-sectional dimension that is less than 90% of the cross-sectional dimension of the fluid barrel and the trigger element is moveable with the plunger rod and extending into the needle chamber of the retraction barrel, the trigger element providing a trigger force causing the needle cannula to retract into the retraction barrel.