What is the recommended approach for initiating insulin therapy in a patient with diabetes?

Insulin Therapy Initiation in Diabetes

Type of Diabetes Determines Initial Approach

For type 1 diabetes, initiate multiple daily injections (MDI) of basal plus prandial insulin or continuous subcutaneous insulin infusion (CSII) immediately at diagnosis, using insulin analogs to reduce hypoglycemia risk 1, 2. For type 2 diabetes, start with basal insulin alone at 10 units daily or 0.1-0.2 units/kg/day while continuing metformin 1, 2, 3, 4.

When to Start Insulin in Type 2 Diabetes

Initiate insulin therapy when:

• HbA1c ≥9% or blood glucose ≥300-350 mg/dL 1, 2
• HbA1c 10-12% with symptomatic hyperglycemia or catabolic features (weight loss, polyuria, polydipsia) 1, 2, 3
• In these severe cases, consider basal insulin plus one mealtime insulin injection as the preferred initial regimen 1

Type 1 Diabetes: Initial Insulin Regimen

Start with approximately one-third of total daily insulin requirements as basal insulin, with the remaining two-thirds as short-acting prandial insulin 1, 4. This typically means:

• Three to four injections daily of basal and prandial insulin 1
• Use insulin analogs (glargine, detemir, or degludec for basal; rapid-acting analogs for prandial) rather than human insulin to reduce hypoglycemia risk 1, 5, 6
• Educate patients to match prandial insulin doses to carbohydrate intake, premeal glucose, and anticipated activity 1, 2

Type 2 Diabetes: Initial Insulin Regimen

Begin with basal insulin only at 10 units once daily or 0.1-0.2 units/kg/day 1, 2, 3, 4. The specific approach:

Starting Dose Selection

• Fixed dose: 10 units once daily for most patients 1, 3, 4
• Weight-based: 0.1-0.2 units/kg/day for those with higher baseline glucose or HbA1c 1, 3, 4
• Continue metformin and possibly one additional non-insulin agent 1, 3

Preferred Basal Insulin Options

• Long-acting analogs (glargine, detemir, or degludec) are preferred over NPH insulin 1, 3, 5, 6
• These analogs reduce nocturnal and overall hypoglycemia risk compared to NPH 1, 5, 6
• Administer once daily at the same time each day, subcutaneously in abdomen, thigh, or deltoid 4

Titration Protocol

Equip patients with a self-titration algorithm based on fasting blood glucose monitoring 1, 2. The standard approach:

• Increase basal insulin by 10-15% or 2-4 units once or twice weekly until fasting glucose target is achieved 1, 2, 3
• Titrate based on fasting glucose values, not postprandial readings 1, 7
• Continue titration until fasting glucose reaches target (typically 80-130 mg/dL) 1

When to Intensify Beyond Basal Insulin

If basal insulin is titrated to acceptable fasting glucose but HbA1c remains above target, advance therapy by:

• First option: Add a GLP-1 receptor agonist (preferred to minimize hypoglycemia and weight gain) 1, 2, 3
• Second option: Add mealtime insulin starting with 4 units, 0.1 units/kg, or 10% of basal dose at the largest meal 1, 2, 3
• Consider fixed-ratio combination products (insulin degludec/liraglutide or insulin glargine/lixisenatide) 1

Medication Management During Insulin Initiation

Continue metformin when starting insulin 1, 3. For other medications:

• Discontinue sulfonylureas, DPP-4 inhibitors, and GLP-1 receptor agonists when advancing beyond basal insulin to more complex regimens 1, 3
• Thiazolidinediones or SGLT2 inhibitors may be continued to reduce total insulin requirements 3
• Never abruptly stop oral medications when starting insulin due to rebound hyperglycemia risk 7

Critical Patient Education Components

Provide comprehensive education on:

• Self-monitoring of blood glucose and using results for dose adjustments 1, 2, 3
• Hypoglycemia recognition, prevention, and treatment 2, 3, 7
• Injection technique: rotate sites within same region to prevent lipodystrophy 4, 7
• The progressive nature of type 2 diabetes and that insulin is not a failure or punishment 1, 2, 3
• For type 1 diabetes: carbohydrate counting and matching prandial insulin to food intake and activity 1, 2

Common Pitfalls to Avoid

Overbasalization

Watch for these warning signs 1, 2:

• Basal dose exceeding 0.5 units/kg 1, 2
• Large bedtime-to-morning glucose differential 1
• Frequent hypoglycemia or high glucose variability 2
• When these occur, add prandial coverage rather than continuing to increase basal insulin 1

Delayed Insulin Initiation

Do not delay insulin therapy in patients failing to achieve glycemic goals 2, 3. The progressive nature of type 2 diabetes means most patients will eventually require insulin 1.

Improper Injection Technique

• Never inject into areas of lipodystrophy or localized cutaneous amyloidosis, as this causes erratic absorption and hyperglycemia 4
• When switching from affected to unaffected injection sites, monitor closely for hypoglycemia 4
• Do not dilute or mix insulin glargine with other insulins 4

Sliding Scale Monotherapy

Traditional sliding-scale insulin regimens are ineffective as monotherapy and should not be used 1. Instead, use scheduled basal and prandial insulin with correction doses as supplements 1.

Administration Specifics

Key technical points 4:

• Administer subcutaneously only—never intravenously or via insulin pump for basal insulin 4
• Inject at the same time daily, though any time of day is acceptable 4
• Rotate injection sites within the same anatomical region 4
• Increase blood glucose monitoring frequency during regimen changes 4