A shielded safety syringe comprising a cylindrical outer sleeve and an inner needle carrier holding a double-pointed needle in fluid communication with a vacuum tube and slidable within the outer sleeve between two positions. In the first position, the needle projects from the outer sleeve and is exposed for drawing blood. In the second position, the needle is retracted within the outer sleeve. The needle carrier is releasably held in the first position so that it can be readily moved into the second position after use. After the needle has been retracted into the sleeve the carrier is locked in its second position to prevent health care workers from coming into accidental contact with the used needle.