The strong effect of magnetic field on the electrochemical (EC) reduction of a diamagnetic species was monitored in situ in a 600 MHz (14 T) NMR spectrometer. Throughout EC-NMR experiments, the diamagnetic species is influenced by the Lorentz force (cross product of current density and magnetic field), which in turn acts on analyte transport and, as a result, enhances reaction rates. This phenomenon, known as magnetoelectrolysis, has not been considered in several in situ EC-NMR studies in solution, electron paramagnetic resonance (EC-EPR) spectroscopy, and magnetic resonance imaging (EC-MRI) involving the oxidation and reduction of organic compounds and lithium ion batteries. Recently, we have demonstrated the presence of this effect in the electroplating of a paramagnetic ion species by monitoring it in situ in a low-field (0.23 T) NMR spectrometer. In this report, a ca. five-fold enhancement in the electroreduction rate of benzoquinone was observed when the analyses were performed in situ in the NMR spectrometer. Therefore, this work has the objective of informing the scientific community that before every electrochemical reaction carried out in situ in NMR, EPR and MRI apparatuses, the influence of the magnetic field on the reactions must be evaluated, since it can alter the mechanism and kinetics of the reaction which, if not taken into account may lead to wrong interpretations of the data.