Impaired Fasting Glucose (IFG) : Introduction

Impaired Fasting Glucose (IFG) is one of the two main forms of prediabetes, characterised by elevated fasting plasma glucose levels that fall below the threshold for type 2 diabetes. It represents a reversible stage in the spectrum of glucose dysregulation, offering primary care clinicians a valuable window for early intervention.

Within the Royal College of General Practitioners (RCGP) curriculum, IFG sits under the module Care of People with Metabolic Problems, highlighting its importance for GPs in identifying at-risk patients, initiating preventative strategies, and reducing long-term complications such as cardiovascular disease and diabetes.

By recognising IFG as a critical intervention point, GPs can help patients reverse or delay disease progression, reduce healthcare burden, and deliver holistic, patient-centred care.

Diagnostic Criteria and Testing

Diagnosis of Impaired Fasting Glucose (IFG) is primarily based on fasting plasma glucose (FPG) measurement. Confirmatory testing on a separate day is recommended to ensure accuracy and exclude transient hyperglycaemia. In selected patients, an oral glucose tolerance test (OGTT) can help identify impaired glucose tolerance (IGT), which often coexists with IFG.

In addition, HbA1c levels between 42–47 mmol/mol (6.0–6.4%) may indicate pre-diabetes, including IFG, though FPG remains central to diagnosis. Recognising these thresholds allows primary...