What is the initial insulin therapy regimen for patients with diabetes?

Initial Insulin Therapy Regimen for Patients with Diabetes

Type 1 Diabetes

Most people with type 1 diabetes should be treated with multiple daily injections of prandial insulin and basal insulin or continuous subcutaneous insulin infusion. 1

Starting Dosage and Regimen

• The starting insulin dose is 0.4 to 1.0 units/kg/day of total insulin, with 0.5 units/kg/day as a typical starting dose in metabolically stable patients 1
• Higher weight-based dosing is required immediately following presentation with ketoacidosis 1
• Approximately one-third of total daily insulin requirements should be basal insulin, with short-acting or rapid-acting insulin analogs covering the remainder as prandial doses 1
• Higher amounts are required during puberty 1

Insulin Type Selection

• Rapid-acting insulin analogs (lispro, aspart, or glulisine) should be used to reduce hypoglycemia risk rather than regular human insulin 1
• Basal insulin options include NPH, glargine, detemir, or degludec 1
• Rapid-acting analogs are administered 0 to 15 minutes before meals 2

Alternative Regimens

• Two or three premixed insulin injections per day may be used as an alternative to basal-bolus therapy 2
• Continuous subcutaneous insulin infusion (insulin pump) is an option with minimal A1C differences compared to multiple daily injections (mean difference favoring pump therapy -0.30% [95% CI -0.58 to -0.02]) 1

Patient Education Requirements

• Education on matching prandial insulin doses to carbohydrate intake, premeal blood glucose levels, and anticipated physical activity should be provided 1

---

Type 2 Diabetes

When to Initiate Insulin

Insulin should be initiated when blood glucose levels are 300-350 mg/dL or greater and/or HbA1c levels are 10-12%, especially if symptomatic or catabolic features are present (in which case basal insulin plus mealtime insulin is the preferred initial regimen). 1

• Consider starting insulin when HbA1c is ≥9% or greater, particularly with dual-regimen combination therapy 1
• Insulin is essential when HbA1c ≥10% (≥86 mmol/mol) after optimal use of diet, physical activity, and other antihyperglycemic agents 2
• Insulin should be used with any combination regimen in newly diagnosed patients when severe hyperglycemia causes ketosis or unintentional weight loss 1

Starting Regimen and Dosage

The preferred method is to begin by adding basal insulin at 10 units or 0.1 to 0.2 units/kg body weight once daily, typically used with metformin and perhaps one additional noninsulin agent 1

• For treatment-naïve patients with type 2 diabetes, the recommended starting dosage is 0.2 units/kg or up to 10 units once daily 3
• Basal insulin options include NPH, glargine, detemir, or degludec 1
• Administer at the same time every day (can be any time of day, but consistency is critical) 3

Titration Protocol

• Increase basal insulin by 2-4 units every 3-7 days until fasting blood glucose reaches target levels 1, 4
• Timely dose titration is important once insulin therapy is initiated 1
• Adjustments should be based on self-monitoring of blood glucose levels 1

Adding Prandial Insulin

When basal insulin has been titrated to appropriate fasting blood glucose levels but HbA1c remains above target:

• Add prandial insulin starting with one injection of rapid-acting insulin (lispro, aspart, or glulisine) at the largest meal 1, 4
• Starting dose is 4 units or 10% of the basal insulin dose 4
• Increase prandial insulin by 1-2 units or 10-15% twice weekly based on postprandial glucose readings 4
• Rapid-acting insulin analogs are preferred because they are faster-acting 1

Severe Hyperglycemia at Presentation

For blood glucose ≥300-350 mg/dL and/or HbA1c 10-12% with symptoms or catabolic features, initiate basal insulin plus mealtime insulin as the preferred initial regimen. 1, 4

Oral Medication Management

• Metformin should be continued when insulin is added, as it is associated with decreased weight gain, lower insulin dose, and less hypoglycemia 1
• SGLT2 inhibitors may be continued to improve glucose control and reduce total daily insulin dose 1, 4
• Thiazolidinediones (usually pioglitazone) may be continued for similar benefits 1
• Sulfonylureas should be withdrawn when more complicated insulin regimens (beyond basal insulin) are used 1, 4
• Dipeptidyl peptidase-4 inhibitors and GLP-1 receptor agonists are usually withdrawn when more complicated insulin regimens are used 1

Alternative: Premixed Insulin

• Twice-daily premixed insulin analogues (70/30 aspart mix or 75/25 or 50/50 lispro mix) may be considered, though their pharmacodynamic profiles make them suboptimal for covering postprandial glucose excursions 1

---

Critical Pitfalls to Avoid

• Do not delay insulin intensification in patients not achieving glycemic goals—this prolongs exposure to severe hyperglycemia and increases complication risk 1, 4
• Do not rely solely on sliding scale insulin without optimizing basal insulin first, as this is ineffective for long-term management 4
• Do not abruptly discontinue oral medications when starting insulin therapy due to risk of rebound hyperglycemia 2
• Avoid intramuscular injections, especially with long-acting insulins, as severe hypoglycemia may result 2
• Rotate injection sites to prevent lipodystrophy, which distorts insulin absorption 3, 2
• When switching from twice-daily NPH to once-daily basal insulin (glargine, detemir, degludec), start at 80% of the total NPH dosage to reduce hypoglycemia risk 1, 3

---

Monitoring Requirements

• Increase frequency of blood glucose monitoring during changes to insulin regimen 3
• Use fasting plasma glucose values to titrate basal insulin 2
• Use both fasting and postprandial glucose values to titrate mealtime insulin 2
• Blood glucose monitoring is an integral part of effective insulin therapy and should not be omitted 2