Recommended Insulin Dosing for Diabetes Management
Type 1 Diabetes
For metabolically stable patients with type 1 diabetes, start with 0.5 units/kg/day total daily insulin dose, divided equally between basal (50%) and prandial insulin (50%), administered via multiple daily injections or continuous subcutaneous insulin infusion. 1
Initial Dosing Strategy
- Total daily insulin requirements typically range from 0.4 to 1.0 units/kg/day 1, 2
- For a 50 kg patient, this translates to approximately 25 units total daily dose (12.5 units basal, 12.5 units divided among meals) 2
- Higher doses are required during puberty, pregnancy, and acute illness 1
- Patients presenting with ketoacidosis require higher weight-based dosing immediately 2
Insulin Regimen Components
- Basal insulin: Administer long-acting insulin analog (glargine, detemir, or degludec) once or twice daily at the same time each day 1, 3
- Prandial insulin: Use rapid-acting insulin analogs (lispro, aspart, or glulisine) 0-15 minutes before each meal to reduce hypoglycemia risk 1, 4
- Educate patients on matching prandial doses to carbohydrate intake, premeal glucose levels, and anticipated physical activity 1
Type 2 Diabetes
For insulin-naive patients with type 2 diabetes, initiate basal insulin at 10 units once daily or 0.1-0.2 units/kg/day, administered subcutaneously at the same time each day, and titrate by 2-4 units every 3 days until fasting blood glucose reaches 80-130 mg/dL. 1, 2, 3
When to Start Insulin
- HbA1c >7% despite optimal oral medications (metformin plus additional agents) 2
- HbA1c ≥9% or blood glucose ≥300-350 mg/dL: consider higher starting doses (0.3-0.4 units/kg/day) 2
- HbA1c 10-12% with symptomatic or catabolic features: start basal-bolus regimen immediately 2
Basal Insulin Titration Algorithm
- Fasting glucose ≥180 mg/dL: Increase by 4 units every 3 days 1, 2
- Fasting glucose 140-179 mg/dL: Increase by 2 units every 3 days 1, 2
- Fasting glucose <80 mg/dL (more than 2 values per week): Decrease by 2 units 2
- Continue titration until fasting glucose reaches 80-130 mg/dL 1, 2
Adding Prandial Insulin
When basal insulin exceeds 0.5 units/kg/day and HbA1c remains above goal despite controlled fasting glucose, add prandial insulin rather than continuing to escalate basal insulin alone. 1, 2
- Start with 4 units of rapid-acting insulin before the largest meal or 10% of the basal dose 1, 2
- Titrate prandial insulin by 1-2 units or 10-15% every 3 days based on pre-meal and 2-hour postprandial glucose readings 2
- Add prandial insulin to additional meals as needed based on glucose patterns 2
Hospitalized Patients (Non-Critical Care)
For hospitalized patients with type 2 diabetes who are insulin-naive or on low-dose insulin, start with a total daily dose of 0.3-0.5 units/kg, with half administered as basal insulin and half as prandial insulin divided among meals. 1, 2
Dosing Adjustments for High-Risk Patients
- Elderly patients (>65 years), renal failure, or poor oral intake: Use lower doses (0.1-0.25 units/kg/day) 1, 2
- Patients on high-dose home insulin (≥0.6 units/kg/day): Reduce total daily dose by 20% to prevent hypoglycemia 2
Basal-Bolus Regimen (Preferred)
- Administer basal insulin once or twice daily 1
- Give rapid-acting insulin before meals, or immediately after meals if oral intake is uncertain 1
- Avoid sliding scale insulin alone as the sole treatment—it is associated with poor glycemic control and is strongly discouraged 1
Critical Care Setting (ICU)
In critically ill patients, use continuous intravenous insulin infusion with validated protocols targeting glucose levels of 140-180 mg/dL for most patients. 1
Glucose Targets
- Most critically ill patients: 140-180 mg/dL 1
- Cardiac surgery patients or acute ischemic events: Consider tighter control (110-140 mg/dL) if achievable without significant hypoglycemia 1
Transitioning from IV to Subcutaneous Insulin
- Ensure stable glucose for at least 4-6 hours consecutively, hemodynamic stability, and stable nutrition plan 1
- Calculate total daily subcutaneous insulin dose as 60-80% of the average 24-hour IV insulin infusion rate 1
- For example, if a patient receives an average of 1.5 units/hour IV insulin, the estimated daily subcutaneous dose is 36 units (1.5 units/hour × 24 hours × 60-80%) 1
- Administer subcutaneous basal insulin 2-4 hours before discontinuing IV insulin to prevent rebound hyperglycemia 1
Administration Guidelines
Injection Technique
- Administer subcutaneously into the abdominal area, thigh, or deltoid 3
- Rotate injection sites to reduce risk of lipodystrophy and localized cutaneous amyloidosis 1, 3
- Use the shortest needles available (4-mm pen or 6-mm syringe needles) to avoid intramuscular injection, which can cause severe hypoglycemia, especially with long-acting insulins 1, 4
Important Precautions
- Do not dilute or mix insulin glargine with any other insulin or solution due to its low pH 2, 3
- Continue metformin when adding insulin therapy unless contraindicated—it reduces weight gain, lowers insulin requirements, and decreases hypoglycemia risk 2, 4
- Monitor blood glucose daily during titration and reassess every 3-6 months once stable 2
Critical Pitfalls to Avoid
Overbasalization
Recognize overbasalization when basal insulin exceeds 0.5 units/kg/day without achieving HbA1c goals—this signals the need for prandial insulin, not further basal insulin escalation. 2
- Clinical signs include: basal dose >0.5 units/kg/day, high bedtime-to-morning glucose differential (≥50 mg/dL), hypoglycemia, and high glucose variability 2
- Continuing to increase basal insulin beyond 0.5-1.0 units/kg/day without addressing postprandial hyperglycemia leads to suboptimal control and increased hypoglycemia risk 2
Hypoglycemia Prevention
- Implement a standardized hospital-wide, nurse-initiated hypoglycemia treatment protocol for blood glucose <70 mg/dL 1
- Review the treatment regimen any time blood glucose <70 mg/dL occurs 1
- If hypoglycemia occurs, determine the cause and reduce insulin dose by 10-20% 2