The disclosed invention provides a self-contained sterilization indicator for evaluating the effectiveness of a sterilization process. The sterilization indicator includes a cap configured for housing a growth medium, the cap being mountable on a container that contains a concentration of microorganisms. The cap comprises an inner chamber for housing the growth media. The inner chamber has an opening and a breakable barrier overlying the opening for encapsulating the growth media within the inner chamber of the cap. The biological indicator is adapted for breaking the breakable barrier at a selected time to introduce the growth medium into the container such that the growth medium contacts the microorganisms.