Function of Beta Cells in Early-onset Diabetes Mellitus

Inclusion Criteria: * The patient is diagnosed with Type 2 Diabetes Mellitus according to the ADA 2024 criteria (Fasting Glucose ≥ 126 mg/dl, or Glucose after 2 hours of an Oral Glucose Tolerance Test ≥ 200 mg/dl, or HbA1C ≥ 6.5%, or with typical symptoms accompanied by any Glucose ≥ 200 mg/dl). * The duration of Type 2 Diabetes Mellitus does not exceed 10 years. * Classification by age of onset: Early onset group (\< 40 years) and typical onset group (≥ 40 years). * At least 6 months without the need for insulin and no recorded episodes of diabetic ketoacidosis since the time of diagnosis. * For the early-onset group: Autoantibodies (Anti-GAD, ICA) are negative and fasting C-peptide levels are \> 0.6 nmol/L. * The patient consents to participate in the study and signs the informed consent document. Exclusion Criteria: * Pregnant women or patients with acute illnesses at the time of assessment. * The patient has been diagnosed with or exhibits characteristics suggestive of Type 1 Diabetes Mellitus (such as a history of ketoacidosis, C-peptide \< 0.2 nmol/L). * Secondary diabetes mellitus due to pancreatic disorders (pancreatitis, pancreatic tumors, pancreatic resection), due to medications (glucocorticoids), or due to other endocrine disorders (Cushing's syndrome, hyperthyroidism, acromegaly). * Severe renal failure with an estimated glomerular filtration rate (eGFR) \< 30 mL/min/1.73 m². * Use of medications that affect beta cell function or complications such as prolonged high-dose corticosteroids, immunosuppressive agents, or chemotherapy. * Not of Vietnamese ethnicity. * Non-compliance with treatment guidelines or failure to attend scheduled follow-up appointments.