Fasting glucose-to-HbA1c ratio is a good indicator of G6PD deficiency, but not thalassemia, in patients with type 2 diabetes mellitus.

Aims: Patients with glucose-6-phosphate dehydrogenase (G6PD) deficiency or thalassemia have a shorter red blood cell lifespan; therefore, HbA1c is underestimated in these patients. To address these issues, we sought an early indicator for G6PD deficiency or thalassemia in DM patients.

Methods: A total of 4908 patients with DM and 1848 subjects without DM were included in this study.