HbA1c % → mmol/mol
Convert HbA1c from NGSP/DCCT percent to IFCC mmol/mol
- IFCC–NGSP master equation
Sources last checked: 2026-10-13
HbA1c % → mmol/mol
Convert HbA1c from NGSP/DCCT percent to IFCC mmol/mol
Converts between reporting units only. HbA1c is unreliable with altered red cell lifespan (haemolysis, recent transfusion, iron deficiency), some haemoglobin variants and advanced CKD.
What is the HbA1c % → mmol/mol?
HbA1c is reported either as a percentage aligned to the DCCT trial (NGSP units) or in mmol/mol from the IFCC reference method. The two are linked by the IFCC–NGSP master equation, based on the method-comparison network described by Hoelzel et al. (2004). European laboratories increasingly report mmol/mol, often alongside the percentage.
When to use it
- Translating a % value into the IFCC unit used in European reports and guidelines
- Comparing results from labs or countries using different units
- Setting or explaining individual HbA1c targets
When not to use it
- Conditions that make HbA1c unreliable: haemolysis, recent blood loss or transfusion, iron deficiency, pregnancy, some haemoglobinopathies
- Converting HbA1c into average glucose — that is a different relationship (eAG)
How it is calculated
HbA1c (mmol/mol, IFCC) = 10.93 × HbA1c (%, NGSP) − 23.50
Clinical pearls and limitations
- Converts between reporting units only. HbA1c is unreliable with altered red cell lifespan (haemolysis, recent transfusion, iron deficiency), some haemoglobin variants and advanced CKD.
- 6.5 % = 48 mmol/mol (diagnostic threshold); 7.0 % = 53 mmol/mol; 8.0 % = 64 mmol/mol.
- IFCC values are whole numbers; report percentages to one decimal place.
- The relation is linear but not proportional — you cannot convert with a simple factor.
Frequently asked questions
How do I convert HbA1c from % to mmol/mol?
mmol/mol = 10.93 × % − 23.5. Example: 7.0 % → 53 mmol/mol.
What is 6.5 % HbA1c in mmol/mol?
48 mmol/mol.
Why are there two HbA1c units?
The percentage reflects the DCCT-aligned NGSP scale; mmol/mol comes from the more specific IFCC reference method, which measures only glycated haemoglobin.
Evidence and guidelines
- Primary source: NGSP. IFCC Standardization of HbA1c — IFCC–NGSP master equation: NGSP (%) = 0.09148 × IFCC (mmol/mol) + 2.152; IFCC = 10.93 × NGSP − 23.50.
- Hoelzel W et al. IFCC reference system for measurement of hemoglobin A1c in human blood and the national standardization schemes in the United States, Japan, and Sweden: a method-comparison study. Clin Chem 2004;50(1):166-174.
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