Hepatitis C virus (HCV) induces insulin resistance, which improves upon viral clearance. Telaprevir is a protease inhibitor effective against HCV genotype 1. We reported a case, whose history suggests that telaprevir may induce some antidiabetic effect independently of its suppression of HCV. A 56-year-old woman with obesity, type 2 diabetes treated with sitagliptin and metformin, and HCV-related cirrhosis was given triple therapy with pegylated interferon-alpha, ribavirin and telaprevir. After 2 weeks of treatment, HCV RNA was no longer detectable but the patient described a pronounced drop in the capillary glucose levels and episodes of hypoglycaemia that compelled her to stop all antidiabetic treatment. One month after stopping telaprevir, she had to resume her antidiabetic treatment, despite a persisting virological response. Despite reaching a sustained virological response, her diabetes progressed. Although the suppression of HCV replication may have played a role in reducing glucose intolerance, the fact that this patient resumed her prior antidiabetic treatment upon completing the telaprevir treatment, while still aviremic, suggests that telaprevir may have an additional antidiabetic effect. Further evidence about the possible role and mechanisms of telaprevir as antidiabetic agent is warranted.