What is the recommended approach to initiate insulin therapy and additional screening tests for a 16-year-old patient newly diagnosed with type 1 diabetes?

Initiating Insulin Therapy in a 16-Year-Old with New Type 1 Diabetes

Start intensive insulin therapy immediately using either multiple daily injections (3-4 injections per day of basal and prandial insulin) or continuous subcutaneous insulin infusion, with rapid-acting insulin analogs for meals and long-acting analogs for basal coverage. 1

Initial Insulin Regimen

Starting Dose Calculation

• Begin with 0.5-1.0 units/kg/day total daily insulin dose 1
• Split approximately 50% as basal insulin and 50% as prandial insulin 2, 3
• Adolescents typically require doses toward the higher end (closer to 1.0 units/kg/day) due to pubertal insulin resistance 1
• If presenting with diabetic ketoacidosis, higher initial doses will be needed after IV insulin is discontinued 2

Insulin Type Selection

• Use rapid-acting insulin analogs (aspart/Novolog, lispro/Humalog, or glulisine/Apidra) for prandial coverage given 0-15 minutes before meals 1, 3

  • These have onset 0.25-0.5 hours, peak 1-3 hours, duration 3-5 hours 1
  • Preferred over regular insulin to reduce hypoglycemia risk 3

• Use long-acting insulin analogs for basal coverage 1, 3

  • Glargine (Lantus/Basaglar/Toujeo): onset 2-4 hours, no peak, duration up to 24 hours 1
  • Detemir (Levemir): onset 2-4 hours, no peak, duration 12-24 hours 1
  • Degludec (Tresiba): onset 2-4 hours, no peak, duration >24 hours 1
  • Administer once daily at the same time each day 4

Administration Details

• Inject subcutaneously into abdomen, thigh, or deltoid 4
• Rotate injection sites within the same region to prevent lipodystrophy 4
• Basal insulin given once daily (typically evening); prandial insulin before each meal 1

Glycemic Targets

• Target A1C <7.5% for adolescents (individualized based on hypoglycemia risk) 1
• Measure A1C every 3 months 1
• Monitor blood glucose frequently during initial stabilization 1
• Consider continuous glucose monitoring to assess time in range and hypoglycemia frequency 1

Essential Patient and Family Education

• Carbohydrate counting to match prandial insulin doses to food intake 3
• Recognition and treatment of hypoglycemia 3
• Sick day management and correction dose calculations 3
• Prescribe glucagon and train family members on administration 3
• Expect a "honeymoon phase" within weeks where insulin needs may temporarily decrease significantly (potentially <0.5 units/kg/day) 1

Additional Screening Tests at Diagnosis

Autoimmune Screening (Perform Soon After Diagnosis)

Celiac Disease Screening 1

• Measure IgA tissue transglutaminase (tTG) antibodies with total serum IgA level 1
• If IgA deficient, measure IgG tTG or deamidated gliadin peptide IgG antibodies 1
• Repeat at 2 years, then at 5 years after diagnosis 1
• Celiac disease occurs in 1-16% of type 1 diabetes patients (vs 0.3-1% general population) 1
• Small bowel biopsy required to confirm diagnosis before starting gluten-free diet 1

Thyroid Screening 1

• Measure anti-thyroid peroxidase (anti-TPO) antibodies (more predictive than anti-thyroglobulin) 1
• Measure TSH once metabolically stable (not at initial diagnosis due to euthyroid sick syndrome from prior hyperglycemia/ketosis) 1
• Recheck TSH every 1-2 years if normal, or sooner if symptoms develop 1
• Autoimmune thyroid disease occurs in 17-30% of type 1 diabetes patients 1
• 25% have thyroid autoantibodies at diagnosis 1

Baseline Metabolic Assessment

Lipid Screening 1

• Obtain fasting lipid profile once glycemic control established (age ≥10 years) 1
• Repeat every 3-5 years if LDL <100 mg/dL 1
• If LDL >160 mg/dL despite 6 months of dietary modification, consider statin therapy (with reproductive counseling due to teratogenicity) 1

Diagnostic Confirmation Tests

• Measure islet autoantibodies (GAD, IA-2, ZnT8) if diagnosis uncertain, particularly in overweight/obese adolescents where type 2 diabetes overlap exists 1, 2
• Consider C-peptide measurement if distinguishing type 1 from type 2 diabetes is challenging 1
• Rule out monogenic diabetes (MODY) in antibody-negative patients, especially with strong family history 1

Common Pitfalls to Avoid

• Do not delay screening tests for celiac and thyroid disease—perform soon after diagnosis when metabolically stable 1
• Do not use NPH insulin as basal insulin; long-acting analogs provide more stable coverage with less nocturnal hypoglycemia 1, 3
• Do not use regular insulin for meals; rapid-acting analogs reduce hypoglycemia risk 1, 3
• Do not administer basal insulin intravenously or via insulin pump (only rapid-acting analogs in pumps) 4
• Do not mix or dilute insulin glargine with other insulins 4
• Do not assume adequate control based solely on A1C—assess for hypoglycemia frequency and glycemic variability 1
• Do not forget to prescribe and educate about glucagon for emergency hypoglycemia treatment 3