A device for adjusting and throttling the flow-rate of a fluid, particularly medical oxygen and compressed gases in general, which comprises a valve body which defines an input port and an output port for a fluid at high pressure; the input port is controlled by a high-pressure flow control element; an input duct is also provided for a low-pressure fluid which is connected to a rotating body with a control port which can be arranged at the calibrated holes provided in an adjustment disk and connected to at least one output duct; a single actuation handwheel is further provided which drives the high-pressure flow control element and the rotating body.