Copper (I, II) oxide powders were tested for glycerol conversion to lactic acid under alkaline conditions. Fresh and spent catalysts were characterized using powder X-ray diffraction, Scanning Electron Microscopy/Energy Dispersive X-ray Spectroscopy, the BET-nitrogen adsorption method and FTIR spectroscopy. In all cases, an almost complete in situ reduction of Cu (I, II) oxides into metallic Cu was observed, even after one catalytic run. Moreover, all the samples of spent catalysts showed similar catalytic activity regardless of their initial form and particle size. Commercial copper powders, prepared copper powders and in situ reduced copper catalysts were tested under the same conditions to compare their catalytic activity. It was shown that the in situ reduced copper catalyst had similar activity to the specially prepared copper powders and much higher activity compared to the commercial copper powders. The in situ reduced copper catalyst exhibited rather high stability. The glycerol conversion and lactic acid selectivity were about 98% and 70%, respectively, after ten catalytic cycles.