A safety arrangement for a medical needle (15) has a support (14) for carrying the mount end of the needle, and a sleeve (16) slidably mounted on the support (14) for movement from an initial position to a retracted position and then back to a protecting position where the sleeve (16) covers the tip (21) of the needle (15). A spring (32) urges the sleeve toward its protecting position and a blocking member (23) projects forwardly from the support (14) and is movable between non-blocking and blocking positions. In the non-blocking position the sleeve (16) is free to slide from its initial position to its retracted position. On movement of the sleeve to its protecting position, the blocking member (23) moves to lie between the support (14) and sleeve (16) to prevent subsequent movement of the sleeve away from its protecting position. A control mechanism (27) releases the blocking member (23) so that it may move from its non-blocking position to its blocking position, the mechanism (27) being controlled by movement of the sleeve (16) from its initial position at least partway towards its retracted position.