In the medicines safety community, one would need to be living under a rock not to have read a great deal about deprescribing by now. Less attention has been devoted to diagnoses, which allow clinicians to make sensible prescribing decisions. In a new slant, the term undiagnosis has been coined to provide a framework for further consideration of this matter. In an interesting discussion (more here), it has been proposed that some diagnoses don’t necessarily attract a need for treatment, as this may create harm without potential benefit. In this discussion it is proposed that diagnoses need to be reviewed periodically – in fact investigations and diagnoses can lead to overdiagnosis, and other factors such as broadening disease definitions and medicolegal apprehension can be drivers. The term undiagnosis, this process facilitates the withdrawal of some medicines. Systematically reviewing diagnoses regularly offers the prospect of reduced prescribing. The authors describe a novel mnemonic: ERASE – Evaluate diagnoses to consider Resolved conditions, Ageing normally and Selecting appropriate targets to Eliminate unnecessary diagnoses and their corresponding medicines. This concept appears to be destined for greater consideration in the future.