We report the detection of the Čerenkov luminescence after the incorporation of a few droplets of a physiological solution of 2-deoxi-2(¹⁸F)fluorine-D-glucose into the ionic liquid 1-Butyl-3-Methylimidazolium Chloride (BmimCl). The phenomenon is attributed to the β⁺ particles having energy above the threshold energy value for the Čerenkov radiation in this medium. The presence of another type of radiation that could eventually cause coincidences in the photodetectors was safely discarded. We show that this property serves to determine the activity of a ¹⁸F solution by means of the novel TDCR-Čerenkov technique. The results were compared with those obtained from the classic TDCR scintillation method using a commercial scintillation cocktail. The activity values obtained from both methods were found to be virtually identical within the experimental uncertainties. The fact that high energy β particles in BmimCl generates Čerenkov photons makes this ionic liquid a promising compound for future research in detection and quantification of ionizing radiation, and it provides a potential alternative for applications in nuclear technology.