Correlations Among BMI, HbA1c, and TyG Index in Type 2 Diabetes Mellitus Patients

Type 2 diabetes mellitus (T2DM) is a chronic metabolic disorder characterized by impaired glucose regulation. Body mass index (BMI) reflects nutritional status, glycated hemoglobin (HbA1c) indicates long-term glycemic control, and the triglyceride-glucose (TyG) index serves as a surrogate marker of insulin resistance. However, evidence regarding the relationships among these parameters in Indonesian patients with T2DM remains limited, particularly in North Jakarta. This study aimed to examine the correlations between BMI and HbA1c, HbA1c and the TyG index, and BMI and the TyG index in patients with T2DM at Hospital X, North Jakarta. This retrospective cross-sectional observational study analyzed 75 medical records of T2DM outpatients treated from January to December 2025 using total sampling. BMI was classified according to Asia-Pacific criteria, while the TyG index was categorized using a cutoff of 4.66. Spearman’s rank correlation was used, with statistical significance set at p < 0.05. The 95% confidence intervals (CIs) were estimated using percentile bootstrap resampling with 5,000 samples. Most patients were female (53.3%), aged 45–54 years (33.3%), and had a T2DM duration exceeding five years (80.0%). Poor glycemic control (HbA1c >8.0%) was observed in 73.3% of patients. BMI showed a weak positive correlation with HbA1c (rs= 0.256, p = 0.027; 95% bootstrap CI: 0.023–0.464). HbA1c also showed a weak positive correlation with the TyG index (rs = 0.258, p = 0.025; 95% bootstrap CI: 0.039–0.453). However, BMI was not significantly correlated with the TyG index (rs = 0.006, p = 0.961; 95% bootstrap CI: −0.218–0.237). In conclusion, BMI and the TyG index were each weakly associated with HbA1c, whereas BMI was not significantly associated with the TyG index. These findings indicate associations rather than causal relationships and suggest that BMI should not be used as the sole indicator of glycemic control.