Hematite is a possible photoanode for photoelectrochemical cells (PECs) that is widely studied using density functional theory (DFT). In this paper we perform more accurate calculations of the absorption spectrum of hematite using the one-shot Green's function (G0W0) and Bethe-Salpeter equation (BSE) methods, which take excited states into account and compare the spectrum to experimental data. We found a match between our calculations and the observed absorption spectra in peak locations. Furthermore, there is anisotropy of the absorption spectra that is concurrent with the crystal structure. We also calculated the absorption spectrum of hematite intermediates during catalysis of the oxygen evolution reaction to better understand which intermediate is dominant during the reaction and the contribution of excited states to catalysis. The *O intermediate was found to be the most optically and chemically dominant species during catalysis.