A safety needle is provided. The safety needle includes a substantially hollow body and a needle assembly that includes a needle supported on a needle hub. The needle hub is movable in relation to the hollow body from an advanced position wherein a sharp tip of the needle extends from the hollow body to a retracted position wherein the sharp tip of the needle is positioned within the hollow body. The safety needle also includes a spring biased retraction mechanism that includes a constant force spring operatively connected to the needle hub. The constant force spring is a generally flat strip of prestressed material that is formed into constant coils around itself. The constant force spring is configured to bias the needle hub towards the retracted position wherein the spring provides a substantially constant force to the needle assembly while the needle assembly moves from the advanced position to the retracted position.