The gas content of a liquid is quickly and reliably controlled by delivering at least one sub-quantity of the liquid into a measurement cell in which a negative pressure is set. A wave-shaped measurement signal is applied to the sub-quantity, and the wave-shaped measurement signal is measured by at least one detector after coming into contact with the sub-quantity of the liquid. A turbidity value of the liquid is determined and compared with a threshold. If the turbidity value is greater than or equal to the threshold, a pressure and a temperature in the measurement cell are measured, and the gas content in the liquid is ascertained using stored characteristics for the solubility of the gas in the liquid dependent on the pressure and temperature.