A method for operating a magneto-inductive flowmeter for measuring the flow velocity or the volume flow of a medium in a measuring tube, wherein, during a supply phase, the medium is supplied by means of at least one coil system of a magnet system with a magnetic field of a first polarity, which magnetic field is essentially perpendicular to a measuring tube axis, wherein the magnetic field is generated by applying an electrical coil voltage to the coil system, wherein the supply phase has a measurement phase with an essentially constant magnetic field; wherein a flow-dependent electric electrode voltage induced in the medium by the magnetic field is tapped by at least two measuring electrodes and output by an output unit; wherein a magnetic field of a following, in particular subsequent, supply phase has a second polarity opposite to the first polarity; wherein the electrode voltage is supplied to an amplifier unit, wherein an amplified electrode voltage is supplied to a first analog/digital converter (54.1); wherein, during the measurement phase, in a first method step, the electrode voltage is used to ascertain a disturbance voltage (StS), wherein, in a second method step, the disturbance voltage is compensated for, wherein the disturbance voltage (StS) is ascertained by means of a digital calculation circuit, wherein the disturbance voltage is readjusted for each supply phase, wherein the electrode voltage of the measurement phase of a supply phase preceding or following the supply phase, in particular a next preceding or next following supply phase, is used to ascertain the disturbance voltage, wherein the digital calculation circuit has a low-pass filter (55.1), wherein the compensation of the electrode voltage is carried out before the electrode voltage is supplied to the amplifier unit by means of an adding/subtracting unit, which adding/subtracting unit has a first signal input for the electrode voltage and a second signal input for a value of the ascertained disturbance voltage. wherein, during a supply phase, the medium is supplied by means of at least one coil system of a magnet system with a magnetic field of a first polarity, which magnetic field is essentially perpendicular to a measuring tube axis, wherein the magnetic field is generated by applying an electrical coil voltage to the coil system, wherein the supply phase has a measurement phase with an essentially constant magnetic field; wherein a flow-dependent electric electrode voltage induced in the medium by the magnetic field is tapped by at least two measuring electrodes and output by an output unit; wherein a magnetic field of a following, in particular subsequent, supply phase has a second polarity opposite to the first polarity; wherein the electrode voltage is supplied to an amplifier unit, wherein an amplified electrode voltage is supplied to a first analog/digital converter (54.1); wherein, during the measurement phase, in a first method step, the electrode voltage is used to ascertain a disturbance voltage (StS), wherein, in a second method step, the disturbance voltage is compensated for, wherein the disturbance voltage (StS) is ascertained by means of a digital calculation circuit, wherein the disturbance voltage is readjusted for each supply phase, wherein the electrode voltage of the measurement phase of a supply phase preceding or following the supply phase, in particular a next preceding or next following supply phase, is used to ascertain the disturbance voltage, wherein the digital calculation circuit has a low-pass filter (55.1), wherein the compensation of the electrode voltage is carried out before the electrode voltage is supplied to the amplifier unit by means of an adding/subtracting unit, which adding/subtracting unit has a first signal input for the electrode voltage and a second signal input for a value of the ascertained disturbance voltage.