What is the recommended insulin dosing regimen for an adult patient with type 2 diabetes (T2D), body mass index (BMI) between 25-35, and no significant comorbidities, to achieve optimal blood glucose control?

Insulin Dosing for Type 2 Diabetes Management

For adults with type 2 diabetes requiring insulin, start with basal insulin at 10 units once daily or 0.1-0.2 units/kg body weight, titrate by 2-4 units every 3 days until fasting glucose reaches 80-130 mg/dL, and add prandial insulin when basal doses exceed 0.5 units/kg/day without achieving glycemic targets. 1, 2

Initial Insulin Initiation Criteria

Start insulin immediately if: 1, 2

• A1C ≥10% (≥86 mmol/mol) with or without symptoms
• Blood glucose ≥300 mg/dL (≥16.7 mmol/L)
• Evidence of catabolism (unexpected weight loss)
• Symptomatic hyperglycemia

For A1C 9-10%, consider starting basal insulin if oral medications plus GLP-1 RA have failed to achieve targets. 1, 3

Basal Insulin Starting Dose

Standard Initiation (A1C <10%)

• 10 units once daily OR 0.1-0.2 units/kg body weight 1, 2, 4
• Administer at the same time each day (bedtime is traditional but any consistent time works) 2, 4
• Continue metformin unless contraindicated 1, 2

Severe Hyperglycemia (A1C ≥10% or glucose ≥300 mg/dL)

• 0.3-0.5 units/kg/day as total daily dose 2, 5
• Split 50% as basal insulin, 50% as prandial insulin divided among three meals 2
• This requires immediate basal-bolus therapy, not basal-only 1, 2

Example calculation for 70 kg patient:

• Standard initiation: 10 units OR 7-14 units (0.1-0.2 × 70 kg)
• Severe hyperglycemia: 21-35 units total daily dose (0.3-0.5 × 70 kg), giving 10-18 units basal + 3-6 units before each meal

Basal Insulin Titration Algorithm

Adjust dose every 3 days based on fasting glucose: 1, 2

Fasting Glucose	Dose Adjustment
≥180 mg/dL	Increase by 4 units
140-179 mg/dL	Increase by 2 units
80-130 mg/dL	No change (target achieved)
<80 mg/dL (≥2 readings/week)	Decrease by 2 units
Hypoglycemia without clear cause	Decrease by 10-20% immediately

Daily fasting blood glucose monitoring is essential during titration. 2

Critical Threshold: When to Stop Escalating Basal Insulin

When basal insulin exceeds 0.5 units/kg/day and approaches 1.0 units/kg/day, adding prandial insulin becomes more appropriate than continuing to escalate basal insulin alone. 1, 2

Signs of "Overbasalization" (indicating need for prandial insulin): 1, 2

• Basal dose >0.5 units/kg/day
• Bedtime-to-morning glucose differential ≥50 mg/dL
• Hypoglycemia episodes
• High glucose variability
• Fasting glucose at target but A1C remains elevated after 3-6 months

Adding Prandial Insulin

Indications: 1, 2

• Basal insulin optimized (fasting glucose 80-130 mg/dL) but A1C >7% after 3-6 months
• Basal insulin dose approaching 0.5-1.0 units/kg/day without achieving A1C goal
• Significant postprandial glucose excursions (>180 mg/dL)

Starting dose: 1, 2

• 4 units of rapid-acting insulin before the largest meal OR
• 10% of current basal dose
• Use rapid-acting analogs (lispro, aspart, glulisine) 0-15 minutes before meals 2, 3

Titration: 2

• Increase by 1-2 units or 10-15% every 3 days based on 2-hour postprandial glucose readings
• Target postprandial glucose <180 mg/dL 6

Alternative to Prandial Insulin

Before advancing to prandial insulin, strongly consider adding a GLP-1 receptor agonist (including dual GIP/GLP-1 RA) to basal insulin. 1 This combination provides:

• Greater glycemic effectiveness than basal insulin alone
• Weight loss rather than weight gain
• Lower hypoglycemia risk compared to basal-bolus insulin
• Reduced insulin dose requirements 1

When adding or escalating GLP-1 RA, reassess and potentially reduce insulin doses. 1

Foundation Therapy

Metformin must continue when starting or intensifying insulin therapy unless contraindicated. 1, 2 Metformin combined with insulin provides:

• Decreased weight gain
• Lower insulin requirements
• Less hypoglycemia compared to insulin alone 3

Maximum effective metformin dose: 2000-2550 mg daily 2

Special Populations Requiring Dose Adjustments

Lower Starting Doses (0.1-0.25 units/kg/day): 2

• Elderly patients (>65 years)
• Renal failure (CKD Stage 5: reduce total daily dose by 50%) 2
• Poor oral intake
• High hypoglycemia risk

Hospitalized Patients: 2

• If on high-dose home insulin (≥0.6 units/kg/day): reduce total daily dose by 20% on admission
• Insulin-naive with moderate hyperglycemia (201-300 mg/dL): 0.2-0.3 units/kg/day
• Severe hyperglycemia (>300 mg/dL): 0.3-0.5 units/kg/day as total daily dose (50% basal, 50% bolus)

Common Pitfalls to Avoid

1. Delaying insulin initiation when oral medications fail to achieve glycemic goals prolongs hyperglycemia exposure and increases complication risk 1, 2

2. Continuing to escalate basal insulin beyond 0.5-1.0 units/kg/day without addressing postprandial hyperglycemia leads to overbasalization with increased hypoglycemia risk and suboptimal control 1, 2

3. Discontinuing metformin when starting insulin leads to higher insulin requirements and more weight gain 1, 2

4. Using sliding scale insulin as monotherapy is explicitly condemned by all major guidelines and shown to be ineffective 2

5. Not adjusting doses frequently enough - basal insulin should be titrated every 3 days during active titration, not weekly or monthly 2

Monitoring Requirements

• Daily fasting glucose during titration phase 2
• Pre-meal and 2-hour postprandial glucose when on prandial insulin 2
• A1C every 3 months during intensive titration 2
• Assess for overbasalization at every clinical visit 1, 2

Patient Education Essentials

Patients must receive training on: 2

• Proper injection technique and site rotation
• Recognition and treatment of hypoglycemia (15g fast-acting carbohydrate for glucose ≤70 mg/dL)
• Self-monitoring of blood glucose
• "Sick day" management rules
• Insulin storage and handling
• Self-titration algorithms based on glucose readings