The invention relates to an injector for transcutaneously introducing asensor into a patient, comprising a cannula, a base element, a sliding elementarranged displaceably on the base element, for transcutaneously introducingthe cannula into the patient in an injection direction, and comprising anejection element for automatically pulling the cannula out of the patientcounter to the injection direction by the ejection element in an ejectionoperation. It is essential that the injector has a locking element for theejection element such that, in a delivery state, the ejection element islockablein an energy-charged state, and in that sliding element and locking elementare designed so as to interact indirectly or directly in order, in aninjectionstate, when the cannula is introduced transcutaneously into the patient, torelease the locking of the ejection element in order automatically to starttheejection operation.
