Reporting HbA1c in SI units

GLYCATED haemoglobin (HbA1c) reporting units are changing from percentage values to SI units of millimoles HbA1c per mole of total haemoglobin (mmol/mol) following the development of a new reference method by the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC).1,2 In Australia, a two year transition period has been proposed, during which old (%) and new (mmol/mol) HbA1c values are reported together.3 HbA1c  percentages will stop being reported at the end of the transition period.

Using the typical HbA1c target of 7% for patients with type 1 or type 2 diabetes, the equivalent target would be 53 mmol/mol in new units.3 Tables and formulae for converting between old and new HbA1c values are available.3,4

Reasons for changing HbA1c reporting values to mmol/mol include: 3-6

• Specificity – the IFCC reference system accurately records HbA1c levels. It is not affected by confounding  haemoglobin-sugar