The invention relates to a metering device (200) for introducing liquid reducing agent into an exhaust gas tract (270), said device comprising a working tank (210) with contents (212), a delivery unit (220) which is connected to the working tank and the delivery direction of which can be reversed and a metering valve (230) which is connected to the delivery unit, is supplied with contents by the delivery unit and is designed to dispense the tank contents in a discharge direction. The metering valve is designed and connected to the delivery unit in such a way that the delivery unit establishes a negative pressure between the delivery unit and the metering valve when the delivery direction is reversed, said negative pressure causing gas to be drawn off through the metering valve against the discharge direction. The invention also relates to a method for operating a metering device for introducing liquid reducing agent into an exhaust gas tract. Said method comprises the steps: providing a delivery unit that is connected to a metering valve and to a working tank; discharging liquid reducing agent by means of a metering valve in a discharge direction. The method comprises the step of emptying the metering valve by drawing gas into an emptying flow direction, which is the opposite direction from the discharge direction, achieved by operating the delivery unit in the opposite direction to that of the delivery direction.