A major challenge when operating a gas lifted unconventional well is severe slugging. Without addressing its root causes, production fluctuation can remain for a long time and pose high risks to the entire operating system. This paper first reviews the gas lift for U.S. unconventional shale plays. Then it describes the major causes of gas lifted shale well slugging and proposes mitigation plans respectively, considering the implications on value and profitability. A systemic diagnostic workflow was developed for shale well slugging by combing production data analytics and dynamic simulation workflow. It also incorporated cost benefit analysis to evaluate incremental economic value. Transient modeling reveals key aspects of gas lift well slugging causes. A case study involving a shale well demonstrates the technical and economic impact of this transient behavior on gas-lift well performance. This study can assist operators in developing a mitigation plan for gas-lifted shale well severe slugging through transient simulation and in leading to substantial cost saving while extending asset economic life. It also demonstrates that transient multiphase flow simulation is an effective tool for the troubleshooting and the mitigation strategy selection for unconventional shale wells under gas lift.