The invention relates to an apparatus for ejecting a fluid having a control unit (510) for controlling the apparatus, the control unit (510) being configured to control fluid dose ejection steps and to determine a priming time length (Tprime), the priming time length (Tprime) being the length of time since the last ejection of a fluid volume through the ejection channel, wherein the control unit (510) is further configured to perform a priming test step (612-618) comprising the steps of: determining whether the priming time length (Tprime) is longer than a predefined priming threshold time length (Tthreshold)； and setting the apparatus into a status, in which a further fluid dose ejection step is only allowed after execution of an ejection channel priming step (622-628) if the priming time length (Tprime) is longer than the priming threshold time length (Tthreshold).
