The aim of this study was to investigate the short-term physiological variation in global cerebral perfusion, oxygen consumption and metabolite concentration, measured by MRI. Global cerebral oxygen consumption as well as N-acetyl-aspartate concentration remain stable over a one-week period. Global cerebral perfusion and lactate concentration was correlated, though showed decreasing within-subject correlation with increasing delay between scan session during the one-week follow-up period. These results should be carefully considered when performing longitudinal studies. In conclusion MRI does provide robust reliable measurements of global cerebral metabolism.