The invention relates to a metering pump having a hydraulic drive (12) for supplying a hydraulic fluid under pressure. The metering pump furthermore comprises a housing (2) and an oscillating piston (3), which is accommodated in the housing (2) in such a way that at least a first and a second hydraulic chamber (9-1, 9-2) and a first (6-1) and a second delivery chamber (6-2) are formed, wherein the oscillating piston (3) has at least a first driving surface (10-1) in the first hydraulic chamber (9-1) and at least a second driving surface (10-2) in the second hydraulic chamber (9-2), and the hydraulic chambers (9-1, 9-2) communicate with the hydraulic drive, thus enabling the oscillating piston (3) to be moved backward and forward between a first and a second position by the hydraulic fluid, wherein, during the movement from the first to the second position, the volume of the first delivery chamber (6-1) is enlarged and the volume of the second delivery chamber (6-2) is reduced and, during the movement from the second to the first position, the volume of the second delivery chamber (6-2) is enlarged and the volume of the first delivery chamber (6-1) is reduced. The invention furthermore relates to a metering system for mixing two fluids and a metering system for metering at least one fluid.