Under what circumstances is HbA1c not suitable for diagnosing diabetes?

HbA1c is not suitable for diagnosing diabetes in children and young people, suspected type 1 diabetes, those who are high risk or acutely ill (e.g. requiring hospital admission), people taking medications that rapidly raise glucose (e.g. steroids, immune checkpoint inhibitors), acute pancreatic damage including pancreatic surgery, and pregnancy.

The circumstances listed in the chapter for when HbA1c should not be used for the diagnosis of diabetes are: all children and young people; suspected type 1 diabetes; high-risk and acutely ill individuals (such as those requiring hospital admission); people taking medication that can cause glucose levels to rise rapidly, including steroids and immune checkpoint inhibitors; acute pancreatic damage, including pancreatic surgery; and pregnancy. Additionally, HbA1c is not suitable for either diagnosis or monitoring when there are genetic, haematological, or illness-related factors that affect its measurement, such as conditions with increased red blood cell turnover (e.g. sickle cell disease, glucose-6-phosphate dehydrogenase deficiency, haemodialysis, recent blood loss or transfusion, and erythropoietin therapy). In these situations, other methods like quality-controlled plasma glucose profiles, total glycated haemoglobin estimation, or fructosamine estimation can be used to assess glycaemia.