Insulin Therapy in Type 2 Diabetes
- Indications:
- Progressive β-cell failure despite oral agents.
- Severe hyperglycemia (e.g., HbA1c >10%).
- Symptoms of hyperglycemia (e.g., polyuria, polydipsia).
- Complications (e.g., DKA, HHS).
- Pregnancy or planned pregnancy.
- Rationale: Insulin is the most effective glucose-lowering therapy, particularly when oral agents fail.
- Types of Insulin:
- Basal Insulin:
- Long-acting (glargine, detemir, degludec).
- Once-daily, peakless, mimics endogenous basal secretion.
- Rationale: Maintains fasting glucose control.
- Prandial Insulin:
- Rapid-acting (lispro, aspart, glulisine).
- Pre-meal administration, mimics postprandial insulin spikes.
- Rationale: Controls postprandial glucose.
- Premixed Insulin:
- Fixed ratios of intermediate/rapid-acting insulin.
- Convenient for patients with fixed meal schedules.
- Rationale: Simplifies dosing for non-complex regimens.
- Basal Insulin:
- Dosing Strategies:
- Basal-Bolus:
- Basal insulin + prandial insulin before meals.
- Titrate based on fasting and postprandial glucose.
- Rationale: Mimics physiological insulin secretion.
- Basal-Plus:
- Basal insulin + 1–2 prandial doses for highest glucose excursions.
- Rationale: Simplifies regimen for patients with mild postprandial spikes.
- Premixed Insulin:
- 1–2 injections/day, fixed ratios (e.g., 70/30).
- Rationale: Suitable for patients with predictable meal patterns.
- Basal-Bolus:
- Monitoring and Adjustments:
- Self-Monitoring:
- Capillary glucose checks (fasting, pre-/postprandial).
- Continuous glucose monitoring (CGM) for tighter control.
- Rationale: Guides titration and detects hypoglycemia.
- HbA1c Targets:
- <7.0% for most, <6.5% for selected patients (e.g., young, no CV disease).
- Rationale: Balances glycemic control and hypoglycemia risk.
- Self-Monitoring:
- Safety Considerations:
- Hypoglycemia:
- Risk increases with sulfonylureas, insulin, and tight control.
- Rationale: Monitor closely, especially in elderly or frail patients.
- Weight Gain:
- Insulin often causes weight gain (1–4 kg initially).
- Rationale: Counteract with lifestyle modifications or GLP-1 RAs.
- Insulin Pumps:
- Continuous subcutaneous insulin infusion (CSII) for tight control.
- Rationale: Flexible, but requires patient education and adherence.
- Hypoglycemia:
- Special Populations:
- Pregnancy:
- Insulin is the preferred therapy (avoid oral agents).
- Rationale: Avoids fetal teratogenicity and achieves tight control.
- Renal/ Hepatic Impairment:
- Adjust doses; avoid certain insulins (e.g., NPH in renal failure).
- Rationale: Clearance is altered; monitor closely.
- Pregnancy:
- Emerging Therapies:
- Inhaled Insulin (Afrezza):
- Rapid-acting, non-invasive, but limited by lung disease.
- Rationale: Alternative for patients with injection aversion.
- Smart Insulin (e.g., Fiasp, Afrezza):
- Ultra-rapid or inhaled options for postprandial control.
- Rationale: Faster onset, shorter duration, reduces hypoglycemia.
- Inhaled Insulin (Afrezza):
- References:
- ADA 2026 Standards of Care (Diabetes Care 2026;49:S321–S338).
- Rationale: Evidence-based guidelines for insulin use in T2DM.
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