Insulin Dosing and Initiation Guidelines
For patients with diabetes, insulin therapy should be initiated with basal insulin at 10 units per day or 0.1-0.2 units/kg per day, with subsequent dose adjustments of 2 units every 3 days until reaching the fasting plasma glucose goal without hypoglycemia. 1
When to Start Insulin Therapy
Consider insulin as first injectable therapy when: 1
- Symptoms of hyperglycemia are present
- A1C >10% (>86 mmol/mol)
- Blood glucose ≥300 mg/dL (≥16.7 mmol/L)
- Type 1 diabetes is suspected
For patients with type 2 diabetes not currently on insulin, the recommended starting dose is 0.2 units/kg or up to 10 units once daily 2
Initial Insulin Dosing Algorithm
For Type 1 Diabetes:
- Start with approximately one-third of total daily insulin requirements as basal insulin 2
- Use short-acting, premeal insulin to satisfy the remainder of daily insulin requirements 2
For Type 2 Diabetes:
Start with basal insulin (long-acting): 1
- Initial dose: 10 units/day OR 0.1-0.2 units/kg/day
- Administer at the same time each day
- Set fasting plasma glucose (FPG) goal based on individualized targets
Titration of basal insulin: 1, 3
- Increase by 2 units every 3 days until reaching FPG goal without hypoglycemia
- For hypoglycemia: determine cause; if no clear reason, lower dose by 10-20%
Insulin Regimen Intensification
If A1C remains above goal after optimizing basal insulin: 1
Adding Prandial Insulin:
- Start with one dose with the largest meal or meal with greatest postprandial glucose excursion 1
- Initial dose: 4 units or 10% of basal insulin dose 1
- Titration: Increase by 1-2 units or 10-15% based on blood glucose response 1
- For hypoglycemia: determine cause; if no clear reason, lower corresponding dose by 10-20% 1
Full Basal-Bolus Regimen:
- Calculate total daily dose (TDD) based on current insulin requirements 1
- Distribute as approximately 50% basal and 50% bolus (mealtime) insulin 1
- Split mealtime insulin evenly between meals 1
- Carbohydrate-to-insulin ratio (CIR) can be estimated as: 4
- 300 ÷ TDD for breakfast
- 400 ÷ TDD for lunch and dinner
Special Considerations
Hospital Setting:
- For enteral/parenteral feedings: 1
- Continue prior basal insulin or calculate from TDD
- For continuous enteral feedings: Add regular insulin every 6 hours or rapid-acting insulin every 4 hours
- For bolus enteral feedings: Give regular or rapid-acting insulin before each feeding
- For parenteral nutrition: Add regular insulin to TPN solution
Perioperative Management:
- Withhold oral hypoglycemic agents the morning of surgery 1
- Give 60-80% of long-acting basal insulin dose 1
- Monitor blood glucose every 4-6 hours while NPO 1
Monitoring and Adjustment
- Assess adequacy of insulin dose at every visit 1
- Equip patients with an algorithm for self-titration based on self-monitoring of blood glucose 1, 5
- Evaluate for signs of overbasalization (elevated bedtime-to-morning glucose differential, hypoglycemia, high glucose variability) 1
- Weekly dose adjustments based on glucose readings alone can be effective and safe when done systematically 5
Common Pitfalls and Caveats
- Failure to titrate insulin doses frequently enough is a common reason for suboptimal control 3
- Patient-managed titration may lead to greater A1C reductions but potentially more hypoglycemia compared to clinic-managed titration 3
- Insulin pump settings are often not selected systematically, leading to suboptimal glucose control 6
- When switching from twice-daily NPH to once-daily basal insulin, start with 80% of the total NPH dose 1, 2
- Patients switching to insulin glargine 300 units/mL from other basal insulins may require lower daily doses while maintaining glycemic control 7
Remember that insulin dosing requires regular monitoring and adjustment based on individual response, with the primary goal of achieving target glycemic control while minimizing the risk of hypoglycemia 1.