What is the initial approach to type 1 diabetes insulin therapy?

Initial Approach to Type 1 Diabetes Insulin Therapy

Start with 0.5 units/kg/day total daily insulin dose, split 50% as basal insulin and 50% as prandial insulin, using rapid-acting insulin analogs for meals and long-acting analogs for basal coverage, delivered via either multiple daily injections or insulin pump. 1, 2

Starting Insulin Dose Calculation

• Calculate total daily dose (TDD) as 0.5 units/kg/day for metabolically stable patients at diagnosis 3, 1, 2
• Divide this dose: 50% as basal insulin (given once daily with glargine or detemir, or via pump) and 50% as prandial insulin (split across meals) 3, 1, 2
• For a 70 kg patient, this equals 35 units total: approximately 17-18 units basal and 17-18 units prandial (divided as ~6 units per meal) 2
• Higher doses (up to 1.0 units/kg/day) are required during puberty, pregnancy, or acute illness 3, 2
• Lower doses (0.2-0.6 units/kg/day) may be appropriate for young children or those in the "honeymoon period" with residual insulin production 2
• Patients presenting with diabetic ketoacidosis require higher initial dosing 2

Insulin Type Selection

• Use rapid-acting insulin analogs (lispro, aspart, or glulisine) for all prandial doses rather than regular human insulin to reduce hypoglycemia risk 3, 1, 4
• Use long-acting basal analogs (glargine or detemir) rather than NPH insulin to minimize nocturnal hypoglycemia and provide more stable 24-hour coverage 1, 5, 4
• Glargine is dosed once daily; detemir may require twice-daily dosing in some patients 3, 6

Delivery Method: Multiple Daily Injections vs. Insulin Pump

• Most patients should use either multiple daily injections (MDI) or continuous subcutaneous insulin infusion (CSII/pump therapy) 3, 1
• MDI regimen: one injection of long-acting basal insulin daily plus rapid-acting insulin before each meal (minimum 4 injections daily) 3, 2
• Pump therapy provides modest advantages with A1C reduction of approximately 0.3% and reduced severe hypoglycemia rates compared to MDI 3
• Automated insulin delivery systems should be considered for all adults when feasible, as they provide superior glycemic control with reduced hypoglycemia 1
• Start with MDI for most patients unless specific indications favor pump therapy (frequent hypoglycemia, high glucose variability, patient preference with adequate resources) 3, 4

Essential Patient Education Before Starting Insulin

• Teach carbohydrate counting as the foundation for prandial insulin dosing 3, 1
• Educate on matching prandial insulin to carbohydrate intake, premeal glucose levels, and anticipated physical activity 3, 1, 2
• For advanced patients, teach adjustment for fat and protein content of meals 1
• Provide education on correction dose calculation based on current glucose and glycemic trends 1
• Train on proper injection technique, including site rotation to avoid lipodystrophy 7
• Prescribe glucagon to all patients and educate family/caregivers on administration for severe hypoglycemia 1, 2
• Cover recognition and treatment of hypoglycemia and sick-day management 3

Injection Technique and Administration

• Administer basal insulin (glargine or detemir) subcutaneously once daily at the same time each day 7
• Inject into abdominal area, thigh, or deltoid, rotating sites within the same region to reduce lipodystrophy risk 7
• Never inject into areas of lipodystrophy, as this causes erratic absorption and hyperglycemia 7
• Administer rapid-acting prandial insulin immediately before meals (0-15 minutes) 1, 4
• Never administer basal insulin intravenously or via insulin pump (applies to glargine specifically) 7
• Do not dilute or mix insulin glargine with any other insulin 7

Monitoring and Titration Strategy

• Increase frequency of blood glucose monitoring during any insulin regimen changes 3, 7
• Titrate basal insulin to achieve fasting glucose targets (typically 80-130 mg/dL) 2
• Adjust prandial insulin based on pre-meal glucose, carbohydrate intake, and post-meal glucose patterns 1
• Reevaluate insulin treatment plans every 3-6 months and adjust as needed 1
• Consider continuous glucose monitoring for all patients, particularly those with hypoglycemia unawareness 1

Common Pitfalls to Avoid

• Avoid using NPH insulin as basal insulin due to pronounced peak effect causing nocturnal hypoglycemia and inadequate duration causing fasting hyperglycemia 5
• Do not use regular human insulin for prandial coverage when rapid-acting analogs are available, as they provide better postprandial control with less hypoglycemia 3, 4
• Never share insulin pens, syringes, or needles between patients due to blood-borne pathogen transmission risk 7
• When switching from twice-daily NPH to once-daily glargine, reduce total dose to 80% of previous NPH dose to avoid hypoglycemia 7
• Recognize that repeated injections into lipodystrophic areas cause hyperglycemia; switching to unaffected areas may cause hypoglycemia requiring dose reduction 7