The Hb A₂-Calderdale variant [δ2(NA2)His→Asn, HBD: c.7C>A] was described as a novel variant in 2014. However, a high performance liquid chromatography (HPLC) peak was never identified indicating that this fraction could be ‘hiding’ somewhere else in the chromatogram. In this case report, we present evidence that the physiochemical properties of Hb A₂-Calderdale resemble those of Hb A_1c, resulting in a coelution in variant mode on the Tosoh G8 but not the Tosoh G11. This coelution results in an overestimation of Hb A_1c and can potentially cause misdiagnosis of type 2 diabetes mellitus (T2DM).