Telomerase reverse transcriptase (TERT) expression is essential for tumor proliferation. Since TERT is exclusively expressed in tumor cells, TERT is also an attractive therapeutic target. However, non-invasive methods of imaging TERT are lacking. Here, we show that TERT expression in preclinical patient-derived brain tumor models is associated with elevated steady-state levels of NADH, an effect that can be non-invasively visualized in vivo by deuterium metabolic imaging using [U-2H]pyruvate. Since 2H-MRS can be readily implemented on clinical MR scanners, our results provide an innovative, clinically translatable method of integrating information regarding a fundamental cancer hallmark, i.e. TERT, into glioma patient management.