What is the recommended starting dosage of subcutaneous regular insulin for a patient with diabetes, and how should it be adjusted based on blood glucose levels?

Subcutaneous Regular Insulin Dosing Guidelines

Initial Dosing for Type 2 Diabetes

For insulin-naive patients with type 2 diabetes, start with 10 units of basal insulin once daily or 0.1-0.2 units/kg body weight, administered at the same time each day. 1

• Continue metformin unless contraindicated, as this combination provides superior glycemic control with reduced insulin requirements and less weight gain 1
• For patients with severe hyperglycemia (HbA1c ≥9%, blood glucose ≥300-350 mg/dL), consider higher starting doses of 0.3-0.5 units/kg/day as total daily insulin using a basal-bolus regimen from the outset 1

Titration Algorithm

Increase basal insulin by 2-4 units every 3 days until fasting blood glucose reaches 80-130 mg/dL:

• If fasting glucose is 140-179 mg/dL: increase by 2 units every 3 days 1
• If fasting glucose is ≥180 mg/dL: increase by 4 units every 3 days 1
• If hypoglycemia occurs without clear cause: reduce dose by 10-20% immediately 1

Critical Threshold: When to Add Prandial Insulin

When basal insulin exceeds 0.5 units/kg/day and approaches 1.0 units/kg/day, add prandial insulin rather than continuing to escalate basal insulin alone. 1

Clinical signals of "overbasalization" include:

• Basal dose >0.5 units/kg/day 1
• Bedtime-to-morning glucose differential ≥50 mg/dL 1
• Episodes of hypoglycemia 1
• High glucose variability throughout the day 1

Adding Prandial Regular Insulin

Start with 4 units of regular insulin 30-45 minutes before the largest meal, or use 10% of the current basal dose: 1, 2

• Regular insulin should be administered 30-45 minutes before meals for optimal postprandial glucose control 2
• Titrate prandial insulin by 1-2 units or 10-15% every 3 days based on 2-hour postprandial glucose readings 1
• Target postprandial glucose <180 mg/dL 1

Type 1 Diabetes Dosing

For type 1 diabetes, start with 0.5 units/kg/day as total daily insulin, divided as 50% basal and 50% prandial insulin split among three meals: 1

• Total daily insulin requirements typically range from 0.4-1.0 units/kg/day 1
• Higher doses are required during puberty, pregnancy, and medical illness 1

Hospitalized Patients: Correction Dosing

For non-DKA hyperglycemia in hospitalized patients, regular insulin can be administered subcutaneously every 6 hours for correction: 2

• In adult patients who are NPO: give supplemental regular insulin in 5-unit increments for every 50 mg/dL increase in blood glucose above 150 mg/dL, up to 20 units for blood glucose of 300 mg/dL 2
• For patients on continuous enteral feedings: use regular insulin every 6 hours for hyperglycemia management 2
• Initiate insulin therapy when blood glucose persistently exceeds 180 mg/dL, targeting 140-180 mg/dL for most hospitalized patients 2

DKA Management

For mild DKA, give an initial "priming" dose of 0.4-0.6 units/kg body weight, followed by 0.1 unit/kg regular insulin subcutaneously or intramuscularly every hour: 2

• For moderate to severe DKA: use continuous intravenous insulin infusion at 0.1 units/kg/hour after an initial IV bolus of 0.15 units/kg 2
• Monitor blood glucose every 1-2 hours during treatment 2
• Continue IV insulin until DKA resolves: glucose <200 mg/dL, bicarbonate ≥18 mEq/L, pH >7.3 2

Transitioning from IV to Subcutaneous Insulin

Administer the first dose of subcutaneous basal insulin 2-4 hours before stopping the IV insulin infusion to prevent rebound hyperglycemia: 3

• Calculate total daily dose based on average IV insulin infusion rate from the 12 hours prior to transition × 24 hours 3
• Give 50% as basal insulin once daily and 50% as prandial insulin divided equally before three meals 3

Common Pitfalls to Avoid

• Never use sliding scale insulin as monotherapy—it leads to dangerous glucose fluctuations and worse outcomes 1, 2
• Never discontinue metformin when starting insulin unless contraindicated, as this leads to higher insulin requirements and more weight gain 1
• Never continue escalating basal insulin beyond 0.5-1.0 units/kg/day without addressing postprandial hyperglycemia, as this causes overbasalization with increased hypoglycemia risk 1
• Never stop IV insulin before administering subcutaneous basal insulin, as this causes rebound hyperglycemia and recurrent DKA 3

Monitoring Requirements

• Daily fasting blood glucose monitoring is essential during titration 1
• Check pre-meal and 2-hour postprandial glucose to guide prandial insulin adjustments 1
• Reassess every 3 days during active titration and every 3-6 months once stable 1