In this work, a 3.5 GHz to 3.9 GHz fast-switchable two-stage GaN Doherty power amplifier with discrete transistors is presented. The amplifier has been designed to be switched to an off-state in order to minimize its power consumption, and is able to turn back on within 37 ns. The lower voltage of the switching circuit is optimized to balance on-state power consumption and off-state input signal leakage to the output. The fabricated GaN Doherty amplifier exhibits a maximum power added efficiency of 59% and a maximum backoff efficiency of 46% at 6 dB backoff while maintaining a saturated output power of 43.8 dBm. Furthermore, the amplifier suppresses the input signal in the off-state up to an input signal level of 30.4 dBm.