Recent studies have focused on the use of ketogenic diet (KD) in the treatment of glioma since tumor cells are heavily glucose-dependent. Here, we assess the ability of MRS to monitor KD-therapy in glioma patients. Using a semi-LASER sequence at 3 T, with fully simulated basis for spectral fitting, we measured increases in acetone and β-hydroxybutyrate after KD in tumor and contralateral brain. NAA concentration decreased in contralateral brain and there was an observed elevation of β-hydroxybutyrate in IDH-mutated gliomas; potentially indicating differential response to KD. These results indicate a potential for MRS in monitoring KD-based therapy in glioma.