Nowadays, with the fast-growing of IoT services, we need to deal with a gigantic amount of requests they generate. To tackle this problem, the next generation 5G network not only utilizes Network Function Virtualization (NFV) to slice one physical network into multiple virtual networks called network slices, to support IoT services of diverse varieties, it also provides scalability on these IoT slices to manage the system capacity according to the incoming demands. This research proposes a hybrid scalability algorithm, designed to perform both vertical and horizontal scalability simultaneously on IoT slices. Previous research supports either vertical or horizontal scalability but rarely combines the applications of both simultaneously. This research designs hybrid scalability and compares its performance with that of either horizontal scalability or vertical scalability alone. The evaluation results show that a hybrid scalability algorithm not only can achieve high efficiency in term of throughput and response time, but also can optimize the resource utilization in terms of CPU utilization and power consumption.