In a 13‑ to 15‑year‑old adolescent with a strong family history of diabetes who presents with polyuria, polydipsia, fasting plasma glucose 8–10 mmol/L and hemoglobin A1c 7.8 %, what is the most appropriate immediate management?

Management of Adolescent with Symptomatic Hyperglycemia

This adolescent with polyuria, polydipsia, fasting glucose 8-10 mmol/L (144-180 mg/dL), and HbA1c 7.8% meets diagnostic criteria for diabetes and requires immediate initiation of basal insulin plus metformin—not additional testing—because the symptomatic presentation with marked hyperglycemia warrants dual pharmacologic therapy at diagnosis. 1

Why Additional Testing (Option A) is Incorrect

• The diagnosis is already established. A fasting glucose ≥7.0 mmol/L (126 mg/dL) OR HbA1c ≥6.5% (48 mmol/mol) confirms diabetes—this patient meets both criteria. 1
• Random blood glucose testing adds no diagnostic value when you already have confirmatory fasting glucose and HbA1c values in a symptomatic patient. 1
• The distinction between prediabetes and diabetes is already clear: prediabetes requires fasting glucose 5.6-6.9 mmol/L (100-125 mg/dL) or HbA1c 5.7-6.4%, neither of which applies here. 1

Why Metformin Alone (Option B) is Insufficient

Metformin monotherapy is only appropriate for asymptomatic or incidentally diagnosed youth with A1C <8.5% (69 mmol/mol). 1 This patient fails both criteria:

• Symptomatic presentation: The presence of polyuria and polydipsia indicates metabolic decompensation requiring more aggressive initial therapy. 1
• HbA1c 7.8% with symptoms: While technically below the 8.5% threshold, the combination of symptoms plus hyperglycemia (fasting glucose up to 10 mmol/L = 180 mg/dL) indicates this patient needs dual therapy. 1

Correct Initial Management: Dual Therapy

Initiate basal insulin at 0.5 units/kg/day while simultaneously starting and titrating metformin. 1, 2

Insulin Component

• Start basal insulin (NPH or long-acting analog like glargine) at 0.5 units/kg/day, typically given once daily at bedtime. 2
• Titrate upward by 2-4 units every 3 days based on fasting blood glucose, targeting 4.4-7.2 mmol/L (80-130 mg/dL). 2

Metformin Component

• Begin metformin 500 mg once daily with dinner for the first week to minimize gastrointestinal side effects. 3, 4
• Increase to 500 mg twice daily after one week, then titrate to target dose of 2,000 mg daily (1,000 mg twice daily) over 2-4 weeks. 3, 2
• Verify renal function (eGFR >30 mL/min/1.73 m²) before starting metformin. 2, 4

Critical Pre-Treatment Assessment

• Rule out ketosis/ketoacidosis by checking serum or urine ketones and venous pH—if present, this requires IV or subcutaneous insulin first to correct metabolic derangement before adding metformin. 1, 2
• Check renal function to ensure metformin safety. 2, 4

Type 1 vs Type 2 Diabetes Considerations

The family history of diabetes and obesity context (implied by type 2 diabetes treatment guidelines being applied) suggest type 2 diabetes, but this distinction can be challenging in adolescents. 1

• If there is diagnostic uncertainty, measure islet autoantibodies (GAD, IA-2) and consider C-peptide levels. 1
• Approximately 10% of adolescents with type 2 diabetes phenotype have islet autoimmunity. 1
• The symptomatic presentation with polyuria/polydipsia can occur in both type 1 and type 2 diabetes. 5, 6, 7

Monitoring and Follow-Up

• Measure HbA1c every 3 months until target <7% (53 mmol/mol) is achieved. 1, 2
• Home blood glucose monitoring before breakfast (fasting) and periodically before other meals and at bedtime. 2
• Once glucose targets are met, insulin can be tapered over 2-6 weeks by decreasing the dose 10-30% every few days while continuing metformin. 1, 2

Essential Lifestyle Interventions

• Refer to registered dietitian for medical nutrition therapy focusing on reduced calorie-dense, nutrient-poor foods, especially sugar-added beverages. 1
• Prescribe at least 150 minutes weekly of moderate-intensity physical activity. 8
• Target 5-7% body weight loss if overweight/obese. 8

Common Pitfalls to Avoid

• Do not delay treatment waiting for additional diagnostic tests—the diagnosis is confirmed and symptoms require immediate intervention. 1
• Do not use metformin monotherapy in symptomatic patients—this prolongs poor glycemic control and increases complication risk. 2
• Do not miss ketoacidosis—always check for ketones in symptomatic hyperglycemic adolescents, as this changes management to immediate insulin therapy. 1