A safety injection needle is an instrument for administering an injection. These needles are designed to reduce the risk of accidental needlestick injuries. They include a needle affixed to a hub and an inner sheath with a slit in it to retain the needle during the injection. The needle and inner sheath are enclosed in an outer sheath that is snap-fitted to the needle hub by snap-fitting snap stoppers.

The protective cover snap is formed in an arcuate trajectory when the force-exerting point A is pressed downward. As the needle is driven into the needle hub, the snap will deform and hold the needle hub hook in place. The force received will determine the hand feeling during the operation. Safety injection needles are available in several designs.

A safety injection needle assembly (100) includes a cap and an outer sheath. The cap can be removable or a permanent locking member can be used. The caps can have indicators that indicate the position of the studs on the outer sheath and cap. Once the needle assembly is in a secure position, the needle can be discarded with no danger of accidental needlestick injuries.

In an alternative embodiment, the injection needle device can include a stretchable member that slides over the needle's protective cover. This allows the needle to be in the desired length. In the initial state, the stretchable member does not connect with the connector. When the holder contracts, the anchoring member of the holder engages the engaging part on the connector.