In which situations should HbA1c not be used for diagnosing diabetes?

HbA1c should not be used to diagnose diabetes in children and young people, when type 1 diabetes is suspected, during acute illness or after severe trauma or a cardiovascular event, or in pregnancy. It is also avoided in people with end-stage renal disease, acute pancreatic damage or pancreatic surgery, those taking medications that can rapidly raise blood glucose such as steroids or antipsychotics, and people with HIV on certain antiviral treatments. Results should be interpreted with caution in conditions affecting red blood cell lifespan, such as anaemia or haemoglobinopathies.

The handbook specifies that a HbA1c test should not be used for diagnosis in all children and young people and in individuals with suspected type 1 diabetes. It should also be avoided during acute illness that requires hospital admission, after severe trauma, or following a cardiovascular event, because severe hyperglycaemia in such settings may be transitory and not diagnostic of diabetes. Pregnancy, end-stage renal disease, acute pancreatic damage including after pancreatic surgery, and treatment for HIV with certain antiviral medications are further situations where HbA1c is not recommended for diagnosis. Additionally, HbA1c results should be interpreted with caution if a person has a condition that causes abnormal red blood cell lifespan, for example anaemia or haemoglobinopathies.