A needle guard, comprising: a housing defining an interior cavity, the housing being configured to accommodate a needle cannula extending through the housing via ports (22, 24) aligned along a longitudinal axis of the housing and defined in opposing ends (18, 20) of the housing; and a transitional member disposed within the interior cavity, the transitional member comprising: a pivoting arm having a first end and a second end, the first end adjacent an interior portion of the housing, a needle tip sensing element configured to contact the needle cannula within the housing when the needle extends through both ports (22, 24) of the housing, and a transverse barrier configured to block the port in the first end of the housing after the needle tip is withdrawn through the interior cavity of the housing past the needle tip sensing element in a distal direction from the first port at the first end of the housing toward the second port at the second end of the housing, wherein the needle tip sensing element is connected to the pivoting arm, and the needle tip sensing element extends radially in a direction toward the needle cannula from and substantially perpendicular to a first side of the pivoting arm adjacent the second end, characterized in that the transverse barrier extends radially outward from and substantially perpendicular to a second side of the pivoting arm adjacent the second end in a direction opposite from a direction in which the needle tip sensing element extends, the first side of the pivoting arm being opposite to the second side. a housing defining an interior cavity, the housing being configured to accommodate a needle cannula extending through the housing via ports (22, 24) aligned along a longitudinal axis of the housing and defined in opposing ends (18, 20) of the housing; and a transitional member disposed within the interior cavity, the transitional member comprising: a pivoting arm having a first end and a second end, the first end adjacent an interior portion of the housing, a needle tip sensing element configured to contact the needle cannula within the housing when the needle extends through both ports (22, 24) of the housing, and a transverse barrier configured to block the port in the first end of the housing after the needle tip is withdrawn through the interior cavity of the housing past the needle tip sensing element in a distal direction from the first port at the first end of the housing toward the second port at the second end of the housing, a pivoting arm having a first end and a second end, the first end adjacent an interior portion of the housing, a needle tip sensing element configured to contact the needle cannula within the housing when the needle extends through both ports (22, 24) of the housing, and a transverse barrier configured to block the port in the first end of the housing after the needle tip is withdrawn through the interior cavity of the housing past the needle tip sensing element in a distal direction from the first port at the first end of the housing toward the second port at the second end of the housing, wherein the needle tip sensing element is connected to the pivoting arm, and the needle tip sensing element extends radially in a direction toward the needle cannula from and substantially perpendicular to a first side of the pivoting arm adjacent the second end, characterized in that the transverse barrier extends radially outward from and substantially perpendicular to a second side of the pivoting arm adjacent the second end in a direction opposite from a direction in which the needle tip sensing element extends, the first side of the pivoting arm being opposite to the second side.