**1. Introduction**

Cystic Fibrosis Related Diabetes (CFRD) is a form of abnormal glucose handling (dysglycae‐ mia) that is quite different to other forms of diabetes. It is uncommon in childhood, rarely occurring in those under 10 years of age, but its incidence rises inexorably as patients survive longer, affecting up to 50% of CF adults [1, 2].

The development of CFRD is associated with a significantly higher mortality rate [2, 3, 4], and has adeleterious impact onpulmonary function[5] withthedegree of glucose intolerance being directly related to the decline in FEV1 [6]. Those with CFRD suffer more frequent infective exacerbations and have a higher burden of colonisation with pathogens such as *Pseudomonas aeruginosa* and *Burkholderia cepacia* as well as a poorer nutritional status – all of which are known to be associated with poorer outcomes [7].

However, dysglycaemia is a progressive phenomenon in many CF patients, and the associat‐ ed increased morbidity occurs many years prior to a formal diagnosis of CFRD [8, 9, 10]. This has fuelled the debate as to how the diagnosis should be made – the current "gold standard" diagnostic test for diabetes mellitus (the oral glucose tolerance test, OGTT) [11] may not be appropriate in the CF population, since the optimal time to introduce treatment (currently limited exclusively to insulin-based therapies) may be at an earlier stage of dysglycaemia.

We will explore these issues as well as consider future developments in this emerging area of CF care.
