CYP2C19*30 is assigned uncertain function due to inadequate evidence. In vitro studies found CYP2C19*30 demonstrated decreased enzyme activity compared to wildtype with mephenytoin, omeprazole, voriconazole, and nebivolol substrates (26153442, 30464555, 29098786). Consensus was not achieved among experts as data were sparse. Therefore, uncertain function was assigned.