What is the recommended approach for initiating insulin therapy in a patient with diabetes, considering factors such as type of diabetes, other medical conditions, and lifestyle modifications?

How to Start Insulin in Type 2 Diabetes

Start basal insulin at 10 units once daily (or 0.1-0.2 units/kg/day) in conjunction with metformin, administered subcutaneously at the same time each day, and titrate by 10-15% (or 2-4 units) once or twice weekly based on fasting blood glucose until target is achieved. 1

When to Initiate Insulin

Insulin should be strongly considered from the outset in the following clinical scenarios 1:

• Symptomatic hyperglycemia with glucose >300-350 mg/dL (16.7-19.4 mmol/L) 1
• HbA1c ≥10.0-12.0% at presentation 1
• Presence of catabolic features (weight loss, muscle wasting) 1
• Ketonuria or ketosis - this is mandatory for insulin initiation 1
• Failure to achieve HbA1c <7% after optimizing oral agents 1

For patients with HbA1c ≥9.0%, starting directly with combination therapy (including insulin) or insulin alone is justified, as monotherapy has low probability of achieving near-normal targets 1.

Specific Starting Regimen

Basal Insulin Initiation

The most convenient and recommended initial approach is once-daily basal insulin 1:

• Starting dose: 10 units once daily OR 0.1-0.2 units/kg/day 1
• Timing: Same time each day (can be any time, but consistency is critical) 1, 2
• Injection sites: Rotate between abdomen, thigh, or deltoid to prevent lipodystrophy 1, 2
• Continue metformin and possibly one additional non-insulin agent 1

Titration Algorithm

Patient education on self-titration improves glycemic control 1:

• Increase dose by 10-15% (or 2-4 units) once or twice weekly until fasting blood glucose target is met 1
• Target fasting plasma glucose: 80-130 mg/dL (ideally <100 mg/dL) 1
• Hold or decrease dose if blood glucose <70-72 mg/dL 1

A more aggressive patient-managed approach: increase by 2 units every 3 days in the absence of hypoglycemia (<72 mg/dL) 3.

Choice of Basal Insulin

Long-acting analogs (glargine U-100, detemir, degludec) reduce nocturnal and symptomatic hypoglycemia compared to NPH, though the advantage is modest 1:

• U-100 glargine or detemir: Standard first-line options 1
• U-300 glargine or degludec: May convey lower hypoglycemia risk when combined with oral agents 1
• NPH insulin: More affordable option when cost is a barrier, though with higher hypoglycemia risk 1

Advancing Beyond Basal Insulin

If basal insulin is titrated to acceptable fasting glucose but HbA1c remains above target, consider adding 1:

• GLP-1 receptor agonist (preferred combination) 1
• Mealtime rapid-acting insulin (lispro, aspart, or glulisine) 1
  • Starting dose: 4 units per meal, 0.1 units/kg per meal, OR 10% of basal dose per meal 1
  • Administer 0-15 minutes before meals 1
  • Consider decreasing basal insulin by the same amount as the starting mealtime dose 1

Critical Patient Education Components

Comprehensive education is mandatory before starting insulin 1:

• Self-monitoring of blood glucose technique and frequency 1
• Insulin injection technique and proper rotation of sites 1, 2
• Hypoglycemia recognition and treatment (symptoms, glucose <70 mg/dL, use of 15g fast-acting carbohydrates) 1
• Sick day management rules 1
• Insulin storage (refrigerate unopened, room temperature for 28 days once opened) 1
• Self-titration algorithms based on home glucose monitoring 1

Common Pitfalls to Avoid

Never present insulin as a threat or punishment - emphasize its utility in maintaining control as the disease progresses 1. Early education about expected disease progression makes the transition easier 1.

Avoid overbasalization - clinical signals include 1:

• Basal dose >0.5 units/kg without adequate fasting glucose control
• High bedtime-to-morning glucose differential (≥50 mg/dL)
• Recurrent hypoglycemia
• High glucose variability

When overbasalization is identified, re-evaluate therapy rather than continuing to escalate basal insulin - consider adding prandial insulin or switching to more concentrated preparations 1.

Do not abruptly discontinue oral medications when starting insulin due to risk of rebound hyperglycemia 4. Specifically:

• Continue metformin (reduces weight gain, lowers insulin requirements, decreases hypoglycemia) 4
• Discontinue sulfonylureas, DPP-4 inhibitors, and GLP-1 agonists only when advancing to complex insulin regimens beyond basal 1

Never share insulin pens, syringes, or needles between patients even if the needle is changed - this poses risk for blood-borne pathogen transmission 1, 2.

Important note for acute presentations: Once hyperglycemic symptoms are relieved in type 2 diabetes, it may be possible to taper insulin partially or entirely and transfer to non-insulin agents 1. This distinguishes type 2 from type 1 diabetes and should be attempted unless there is evidence of absolute insulin deficiency.