Background: Red blood cell distribution width (RDW), a hematologic index, is a quantitative measure of the range in volume and size of red blood cells. Hyperglycemia in patients with type 2 diabetes is considered to promote the formation of glycosylated hemoglobin (HbA1C) and to shorten the lifespan of red blood cells by reducing their deformability and increasing their osmotic fragility and adhesiveness. Objectives: To evaluate the association between red cell distribution width (RDW), mean corpuscular volume (MCV), and mean corpuscular hemoglobin content (MCHC) of red blood cells and glycemic control in patients with type 2 diabetes. Methods: This retrospective study included 107 patients with type 2 diabetes who were undergoing treatment at Tien Giang General Hospital from April to August 2019. Gender, age, complete blood count, plasma glucose, HbA1C, cholesterol, and triglyceride data were collected. The patients were divided into two groups: group I (HbA1C≤6.5–6.9%; n=51) and group II (HbA1C≥7.0%; n=56). Results: RWD was 13.32 for the group I and 13.95 for group II. MCHC was 32.21 for the group I and 32.84 for group II. RDW and MCHC were significantly higher in patients without good glycemic control (HbA1C≥7.0%) than with good HbA1C control (6.5–6.9%). RDW showed a significant correlation between glucose concentration and MCHC. HbA1C and MCHC were also significantly correlated. Conclusion: Good glycemic control is associated with lower RDW and MHC values in patients with type 2 diabetes. Therefore, RDW and MCHC can be used as prognostic markers to assist in blood glucose control in these patients.