Insulin injections have never been an entirely satisfactory therapy, and as a result a continuing 'biobetter' technological cascade has driven changes in purity and manufacture, in structure and excipients, and in administration devices. The resulting deck of insulin preparations has to be matched by health-care teams and users with individual need. This latter is itself a complex ranging from ambulatory care in type 1 and type 2 diabetes, the topic generally addressed by guidelines and funding advice, to in-patient care and the newly diagnosed, plus secondary diabetes with very different effects on insulin need, through to co-morbidities and medications interfering with glucose metabolism. In this article the match of different clinical scenarios to the available insulins is discussed in the context of available evidence, quality guidelines, and diabetes best practice. Additionally the role of biosimilars of the insulin analogues is addressed, their limited but useful price advantage, and the management consequences of substitution for the originator product.