The drug calculation skill of nurses continues to be a national concern. The continued concern has led to the introduction of mandatory drug calculation skills tests which students must pass in order to go on to the nursing register. However, there is little evidence to demonstrate that nurses are poor at solving drug calculation in practice. This paper argues that nurse educationalists have inadvertently created a problem that arguably does not exist in practice through use of invalid written drug assessment tests and have introduced their own pedagogical practice of solving written drug calculations. This paper will draw on literature across mathematics, philosophy, psychology and nurse education to demonstrate why written drug assessments are invalid, why learning must take place predominantly in the clinical area and why the key focus on numeracy and formal mathematical skills as essential knowledge for nurses is potentially unnecessary.