Prediabetes is a term that embraces various states of hyperglycaemia that fall short of reaching the criteria for diabetes.
The condition encompasses impaired fasting glucose and impaired glucose tolerance, and some clinicians would also include gestational diabetes.
In part, the term has arisen because of the shift in diagnostic testing preference from fasting glucose and oral glucose tolerance tests to using glycated haemoglobin (HbA1c).
The usual evolution of type 2 diabetes is from normoglycaemia through prediabetes to a formal diagnosis of diabetes. Progression is not, however, inevitable and for this reason the term prediabetes has been said to be misleading. Alternative terms have been proposed, including intermediate hyperglycaemia, impaired glucose regulation, and, the RCGP favoured term, non-diabetic hyperglycaemia.1
In line with WHO recommendations to adopt HbA1c as the primary diagnostic test for diabetes,2 the most pragmatic and convenient method for defining prediabetes is an HbA1c of 42–47 mmol/mol (6–6.4 per cent), the diagnostic threshold for diabetes being 48 mmol/mol. These recommendations have been conveniently summarised.3