Continuous glucose monitoring reveals improved hyperglycemia and altered hypoglycemia target attainment after gastrectomy in patients with type 2 diabetes

This study aimed to investigate glycemic variability and biochemical profiles before and after gastrectomy using continuous glucose monitoring (CGM) and to evaluate whether postoperative improvements occur in blood glucose levels and biochemical parameters. We analyzed data from patients who underwent surgery for gastric cancer. Glucose profiles were assessed using a CGM device before gastrectomy and after discharge. All patients discontinued antidiabetic medications one day before surgery and resumed them only after reassessment at outpatient follow-up. CGM-derived metrics were evaluated according to international consensus recommendations, including time above range (TAR), time below range (TBR), time in range (TIR), CV (coefficient of variation), and MAGE (mean amplitude of glycemic excursions). A total of 33 patients were included. The mean duration of diabetes was 16.9 ± 10.4 years, and 12.1% were receiving insulin therapy. Mean glucose levels and TAR significantly decreased after gastrectomy while TIR significantly increased. Although TBR did not increase significantly, adherence to hypoglycemia targets worsened postoperatively. Glucose variability, assessed by CV, remained stable. Also, most patients maintained CV values below the threshold for glycemic instability. MAGE significantly decreased after surgery, indicating a reduction in large-amplitude glucose excursions. Among 16 patients whose postoperative medication changes were evaluated, seven (43.8%) reduced their antidiabetic medication after gastrectomy. In conclusion, despite the temporary discontinuation of antidiabetic medications, hyperglycemia improved without aggravation of glycemic variability, as reflected by increased TIR, stable CV and reduced MAGE. However, the achievement of hypoglycemia targets was reduced. Therefore, instead of routinely resuming preoperative antidiabetic regimens, postoperative glucose management should be individualized based on CGM-derived glycemic profiles.