What is the recommended approach for initiating insulin therapy in a patient with type 2 diabetes, considering their overall medical condition, including potential impaired renal (kidney) function or other comorbidities?

How to Start Insulin in 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, continue metformin unless contraindicated, and titrate the dose by 2-4 units every 3 days until fasting blood glucose reaches 80-130 mg/dL. 1

Initial Dosing Strategy

For most insulin-naive patients with type 2 diabetes, begin with 10 units of long-acting basal insulin (such as glargine, detemir, or degludec) once daily. 1 Alternatively, use weight-based dosing of 0.1-0.2 units/kg/day for the initial dose. 1

Higher Starting Doses for Severe Hyperglycemia

• If HbA1c ≥9%, blood glucose ≥300-350 mg/dL, or the patient has symptomatic/catabolic features (weight loss, ketosis), start with basal-bolus insulin immediately rather than basal insulin alone. 1, 2
• For marked hyperglycemia without catabolic features, consider more aggressive starting doses of 0.3-0.5 units/kg/day as total daily dose. 1, 2, 3
• Split this total dose: 50% as basal insulin once daily and 50% as rapid-acting insulin divided among three meals. 1, 2

Lower Starting Doses for High-Risk Patients

• For elderly patients (>65 years), those with renal impairment, or poor oral intake, start with lower doses of 0.1-0.25 units/kg/day to prevent hypoglycemia. 2

Foundation Therapy: Continue Metformin

Always continue metformin when initiating insulin unless contraindicated (such as eGFR <30 mL/min/1.73m²). 1 Metformin reduces insulin requirements, limits weight gain, and provides complementary glucose-lowering effects. 1, 2

• Consider continuing one additional non-insulin agent, but discontinue sulfonylureas when advancing beyond basal-only insulin to prevent hypoglycemia. 1

Titration Algorithm

Increase basal insulin by 2-4 units (or 10-15%) once or twice weekly based on fasting blood glucose values until reaching target of 80-130 mg/dL. 1, 2

Specific Titration Schedule

• If fasting glucose ≥180 mg/dL: increase by 4 units every 3 days 2
• If fasting glucose 140-179 mg/dL: increase by 2 units every 3 days 2
• If fasting glucose <80 mg/dL on more than 2 occasions per week: decrease by 2 units 2
• If hypoglycemia occurs without clear cause: reduce dose by 10-20% immediately 2

Patient Self-Titration

Empower patients with self-titration algorithms based on self-monitoring of blood glucose, as this improves glucose control. 1 Most patients can be taught to uptitrate their own insulin dose by 1-2 units (or 5-10% for higher doses) once or twice weekly if fasting glucose remains above target. 2

Critical Threshold: Recognizing When to Add Prandial Insulin

When basal insulin exceeds 0.5 units/kg/day and approaches 1.0 units/kg/day, stop escalating basal insulin and add prandial insulin instead. 1, 2 Continuing to increase basal insulin beyond this threshold leads to "overbasalization" with increased hypoglycemia risk and suboptimal control. 1, 2

Clinical Signs of Overbasalization

• Basal insulin dose >0.5 units/kg/day 2
• Bedtime-to-morning glucose differential ≥50 mg/dL 2
• Hypoglycemia episodes 2
• High glucose variability 2
• Fasting glucose at target but HbA1c remains elevated after 3-6 months 1

Adding Prandial Insulin

Start with 4 units of rapid-acting insulin (lispro, aspart, or glulisine) before the largest meal, or use 10% of the current basal dose. 1, 2 If HbA1c <8%, this is the recommended starting dose. 1

• Consider decreasing the basal insulin dose by the same amount as the starting mealtime dose. 1
• Titrate prandial insulin by 1-2 units or 10-15% every 3 days based on postprandial glucose readings. 2

Alternative: GLP-1 Receptor Agonist Combination

Consider adding a GLP-1 receptor agonist to basal insulin instead of prandial insulin to address postprandial hyperglycemia while minimizing weight gain and hypoglycemia risk. 1, 2 The FDA has approved fixed-ratio combination products containing basal insulin plus GLP-1 receptor agonist (lixisenatide/glargine and liraglutide/degludec). 1

Patient Education Requirements

Provide comprehensive education on blood glucose monitoring, hypoglycemia recognition and treatment, nutrition, and insulin injection technique before initiating insulin. 1

• Teach proper insulin injection technique and site rotation to prevent lipohypertrophy. 2, 4
• Educate on "sick day" management rules and insulin storage/handling. 2
• Avoid threatening patients with future insulin therapy during earlier stages of diabetes, as this makes the transition more difficult. 1

Special Considerations for Renal Impairment

In patients with renal impairment, start with lower insulin doses and monitor closely for hypoglycemia, as insulin clearance is reduced. 2 Initial doses of 0.1-0.25 units/kg/day are appropriate for high-risk patients with kidney disease. 2

Cost Considerations

While newer long-acting insulin analogues cause less hypoglycemia, intermediate-acting NPH insulin may be a more affordable option for some patients. 1 Consider cost when selecting an insulin product, particularly given substantial price increases over the past decade. 1

Common Pitfalls to Avoid

• Never delay insulin initiation in patients not achieving glycemic goals with oral medications, as this prolongs exposure to hyperglycemia and increases complication risk. 1, 2
• Do not continue escalating basal insulin beyond 0.5-1.0 units/kg/day without addressing postprandial hyperglycemia with prandial insulin or GLP-1 receptor agonist. 1, 2
• Do not abruptly discontinue oral medications when starting insulin; continue metformin unless contraindicated. 2, 4
• Avoid using correction insulin ("sliding scale") alone without scheduled basal insulin, as this approach is inferior to basal-bolus regimens. 2