Type 1 and Type 2 Diabetes

A 28-year-old woman presents with a 3-week history of polyuria, polydipsia, and weight loss. Fasting blood glucose is 245 mg/dL and random blood glucose is 312 mg/dL. She has no family history of diabetes. Which investigation is most appropriate to differentiate between Type 1 and Type 2 diabetes in this patient?

All of the following are features that differentiate Type 1 diabetes mellitus from Type 2 diabetes mellitus EXCEPT:

A 28-year-old man presents with a 2-week history of polyuria, polydipsia, and weight loss of 3 kg. On examination, he appears acutely unwell with Kussmaul respiration. Blood glucose is 450 mg/dL, arterial pH 7.25, HCO₃⁻ 12 mEq/L, and serum ketones are positive. C-peptide is undetectable. What is the most appropriate immediate next step in management?

A 52-year-old woman with a 5-year history of Type 2 diabetes mellitus is reviewed in the outpatient clinic. Current medications: metformin 1000 mg BD, glipizide 5 mg BD. Recent HbA1c is 8.2% (target < 7%), fasting glucose 160 mg/dL, postprandial glucose 220 mg/dL. She has no contraindications to additional agents. Urine albumin-to-creatinine ratio is 45 mg/g (normal < 30). What is the most appropriate next step in management?

Which clinical feature best distinguishes Type 1 diabetes mellitus from Type 2 diabetes mellitus in a newly diagnosed Indian patient?