What is the initial insulin therapy regimen for patients with diabetes?

Initial Insulin Therapy Regimen for Diabetes

For type 2 diabetes patients requiring insulin, start with basal insulin at 10 units once daily or 0.1-0.2 units/kg body weight, administered at the same time each day, typically in conjunction with metformin. 1, 2, 3

Type 1 Diabetes: Basal-Bolus Regimen Required

Type 1 diabetes mandates a basal-bolus regimen from diagnosis, with approximately one-third of total daily insulin requirements (typically 0.5 units/kg/day) given as basal insulin and the remainder as rapid-acting prandial insulin before meals. 1, 2, 3, 4

• Total daily insulin requirements typically range from 0.4-1.0 units/kg/day, with 0.5 units/kg/day being standard for metabolically stable patients 2, 3
• Divide the total dose: 40-50% as basal insulin (glargine, detemir, degludec, or NPH) once or twice daily, and 50-60% as rapid-acting insulin (lispro, aspart, or glulisine) split among three meals 1, 2, 3
• Rapid-acting insulin must be administered 0-15 minutes before meals, not after eating 2, 4
• Patients in the "honeymoon phase" with residual beta-cell function may require lower doses of 0.2-0.6 units/kg/day 2

Type 2 Diabetes: Stratified Approach Based on Severity

Mild-to-Moderate Hyperglycemia (A1C <9%)

Begin with basal insulin alone at 10 units once daily or 0.1-0.2 units/kg body weight, continuing metformin and possibly one additional non-insulin agent. 1, 2, 3

• Administer at the same time each day (morning, evening, or bedtime—consistency matters more than timing) 1, 3
• Titrate by 2-4 units (or 10-15%) once or twice weekly until fasting blood glucose reaches 80-130 mg/dL 1, 2, 5
• If fasting glucose ≥180 mg/dL, increase by 4 units every 3 days; if 140-179 mg/dL, increase by 2 units every 3 days 2, 5
• Equip patients with self-titration algorithms based on self-monitored blood glucose to improve glycemic control 1

Severe Hyperglycemia (A1C ≥9-10% or Blood Glucose ≥300-350 mg/dL)

Consider starting at a higher initial dose or immediately initiating basal-bolus therapy, especially if symptomatic or showing catabolic features (weight loss, polyuria, polydipsia). 1, 5

• For severe hyperglycemia with symptoms: start basal insulin at 0.2-0.4 units/kg/day plus 4 units of rapid-acting insulin before the largest meal 1, 2, 5
• For A1C ≥10-12% with symptomatic/catabolic features: basal-bolus insulin is the preferred initial regimen 1, 5
• Continue or initiate metformin unless contraindicated, as it reduces insulin requirements, limits weight gain, and decreases hypoglycemia risk 1, 2, 5

Youth with Type 2 Diabetes

For youth with A1C ≥8.5% without acidosis or ketosis, start basal insulin at 0.5 units/kg/day in addition to metformin, titrating every 2-3 days based on blood glucose monitoring. 1

• If ketoacidosis or marked ketosis is present, initiate insulin therapy immediately until fasting and postprandial glycemia normalize, then add metformin 1
• If random blood glucose ≥250 mg/dL or A1C ≥8.5%, start with insulin even when the distinction between type 1 and type 2 diabetes is unclear 1

Critical Titration Principles

Daily fasting blood glucose monitoring is essential during titration, with dose adjustments every 3 days until target fasting glucose (80-130 mg/dL) is achieved. 1, 2, 5

• If hypoglycemia occurs, determine the cause and reduce the dose by 10-20% immediately 2, 5
• If more than 2 fasting glucose values per week are <80 mg/dL, decrease basal insulin by 2 units 2
• Reassess A1C every 3 months once stable 5

When to Advance Beyond Basal Insulin

If basal insulin has been titrated to achieve acceptable fasting glucose (80-130 mg/dL) but A1C remains above target after 3-6 months, add prandial insulin or a GLP-1 receptor agonist to cover postprandial glucose excursions. 1, 2

• When basal insulin exceeds 0.5 units/kg/day and approaches 1.0 units/kg/day without achieving A1C goals, add mealtime insulin rather than continuing to escalate basal insulin alone 2, 5
• Start prandial insulin with 4 units of rapid-acting insulin before the largest meal (or 10% of the basal dose), titrating by 1-2 units or 10-15% every 3 days based on postprandial glucose readings 1, 2, 5
• Alternative: add a GLP-1 receptor agonist to improve A1C while minimizing weight gain and hypoglycemia risk 1, 5

Administration Guidelines

Administer insulin subcutaneously into the abdominal area, thigh, or deltoid, rotating injection sites within the same region to reduce lipodystrophy risk. 3

• Do not administer intravenously, via insulin pump (for glargine), or mix/dilute with other insulins or solutions 3
• Visually inspect for particulate matter and discoloration; use only if clear and colorless 3
• Never share insulin pens, syringes, or needles between patients due to blood-borne pathogen transmission risk 3

Common Pitfalls to Avoid

Delaying insulin initiation in patients not achieving glycemic goals with oral medications increases morbidity and mortality risk. 2, 5

• Overbasalization: Continuing to increase basal insulin beyond 0.5-1.0 units/kg/day without addressing postprandial hyperglycemia leads to suboptimal control and increased hypoglycemia risk 2, 5
• Clinical signals of overbasalization include: basal dose >0.5 units/kg/day, bedtime-to-morning glucose differential ≥50 mg/dL, hypoglycemia episodes, and high glucose variability 2
• Not adjusting doses based on self-monitoring results leads to poor glycemic control 2
• Injecting into areas of lipodystrophy causes erratic absorption and hyperglycemia; sudden site changes to unaffected areas can cause hypoglycemia 3

Foundation Therapy Maintenance

Continue metformin when initiating or intensifying insulin therapy unless contraindicated, as it remains the foundation of type 2 diabetes management and reduces insulin requirements. 1, 2, 5

• Metformin combined with insulin decreases weight gain, lowers insulin dose requirements, and reduces hypoglycemia compared to insulin alone 4
• Do not abruptly discontinue oral medications when starting insulin due to rebound hyperglycemia risk 4