There is a growing interest in assessment of future remnant liver function with Tc-mebrofenin hepatobiliary scintigraphy before major hepatectomy to estimate the risk of posthepatectomy liver failure. We illustrate the case of a 42-year-old woman with liver metastasis from colorectal cancer who performed hepatobiliary scintigraphy. Tc-mebrofenin clearance rate of the total liver was considerably low. The patient recently started a treatment for active hepatitis C with a combination of 2 new direct-acting antiviral agents (grazoprevir, elbasvir). Apart from hypoalbuminemia or hyperbilirubinemia, physicians must be aware that drug interactions can interfere with Tc-mebrofenin liver uptake, thereby resulting in a dramatic underestimation of liver function.