Structural hemoglobin variants can affect the accuracy of hemoglobin A1c (HbA1c) testing and represent the most common pitfall in the determination of HbA1c. We here describe the characterization of an alpha chain variant in diabetic patients as the cause of an abnormal presentation of the HbA1c fraction on the HLC-723 G7 analyzer.HbA1c analysis was performed using various HPLC-based HbA1c analyzers and by immunoassay. alpha-Globin mutation analysis was performed by GAP-PCR and DNA sequencing.The peak partially overlapping HbA1c in the chromatogram represents the glycated fraction of the silent alpha chain variant Hb Riccarton [alpha51(CE9)Gly-->Ser]. This aberrant peak is uniquely identified by the HLC-723 instrument, as it is not observed on other HPLC-based HbA1c analyzers. Occasionally, the HLC-723 may fail to properly integrate both glycated Hb fractions, resulting in a falsely low HbA1c result. The variant was confirmed in samples from other diabetic patients with identical chromatographic patterns.The silent alpha chain variant Hb Riccarton [alpha51(CE9)Gly-->Ser] leads to an abnormal chromatographic presentation on the HLC-723 analyzer with a risk of erroneous HbA1c determination. Manual validation of chromatograms to detect abnormalities caused by Hb variants is important to prevent incorrectly produced HbA1c results from being reported.