What is the recommended dose of insulin (intravenous/ subcutaneous injection of insulin) for a patient with diabetes?

Recommended Insulin Dosing

For type 1 diabetes, start with 0.5 units/kg/day total daily dose, with half as basal insulin and half as prandial insulin; for type 2 diabetes, initiate basal insulin at 10 units once daily or 0.1-0.2 units/kg/day, then titrate by 2-4 units every 3 days until fasting glucose reaches 80-130 mg/dL. 1, 2, 3

Type 1 Diabetes Dosing

Initial Dosing

• Total daily insulin requirement ranges from 0.4-1.0 units/kg/day, with 0.5 units/kg/day being the typical starting dose for metabolically stable patients 1, 2
• Split the total daily dose equally: 50% as basal insulin and 50% as prandial insulin distributed across meals 1
• Higher doses are required during puberty, pregnancy, and acute medical illness 1
• Patients presenting with ketoacidosis require higher weight-based dosing initially 2

Administration Method

• Multiple daily injections (MDI) or continuous subcutaneous insulin infusion (CSII) are the preferred treatment approaches 1
• Use rapid-acting insulin analogs (lispro, aspart, or glulisine) before meals to reduce hypoglycemia risk 1
• CSII provides modest advantages with A1C reduction of -0.30% and reduced severe hypoglycemia rates compared to MDI 1

Prandial Insulin Adjustment

• Educate patients to match prandial insulin doses to carbohydrate intake, premeal glucose levels, and anticipated physical activity 1
• The carbohydrate-to-insulin ratio equals 300 divided by total daily dose at breakfast, or 400 divided by total daily dose at lunch and dinner 4

Type 2 Diabetes Dosing

Initial Basal Insulin Therapy

• Start with 10 units once daily or 0.1-0.2 units/kg/day of long-acting basal insulin 1, 2, 3
• Administer at the same time each day 2, 3
• Continue metformin and other oral agents when initiating insulin 1, 2

Titration Protocol

• Increase dose by 2-4 units every 3 days until fasting glucose reaches target of 80-130 mg/dL 1, 2
• If fasting glucose ≥180 mg/dL, increase by 4 units every 3 days 2
• If fasting glucose 140-179 mg/dL, increase by 2 units every 3 days 2
• Alternative approach: increase by 10-15% or 2-4 units once or twice weekly 2

When to Add Prandial Insulin

• When basal insulin exceeds 0.5 units/kg/day and A1C remains elevated despite controlled fasting glucose, add prandial insulin rather than continuing to escalate basal insulin 2
• Start with 4 units of rapid-acting insulin before the largest meal, or 10% of the basal dose 1, 2
• This prevents "overbasalization" which causes hypoglycemia and high glucose variability 2

High-Risk Patients

• Use lower doses (0.1-0.25 units/kg/day) for elderly patients (>65 years), those with renal failure, or poor oral intake 1, 2

Hospitalized Patients

Critical Care Setting

• Continuous intravenous insulin infusion is the preferred method for achieving glycemic targets in critically ill patients 1
• Use validated written or computerized protocols for dose adjustments 1
• Target glucose range of 140-180 mg/dL for most critically ill patients 1

Non-Critical Care Setting

• For insulin-naive or low-dose patients, start with 0.3-0.5 units/kg/day total daily dose, with half as basal insulin 1, 2
• For patients on high-dose home insulin (≥0.6 units/kg/day), reduce total daily dose by 20% to prevent hypoglycemia 2
• Use basal-bolus regimen (basal insulin plus prandial insulin before meals) for patients with good nutritional intake 1
• Use basal-plus-correction regimen for patients with poor oral intake or nothing by mouth 1
• Sliding-scale insulin alone is strongly discouraged and should not be used 1

Transitioning from IV to Subcutaneous Insulin

• Calculate subcutaneous dose from the average insulin infused during the 12 hours before transition 1
• For a patient receiving 1.5 units/hour, the estimated daily dose is 36 units/24 hours 1
• Give subcutaneous insulin 1-2 hours before discontinuing IV insulin 1
• Convert to basal insulin at 60-80% of the daily infusion dose 1

Enteral/Parenteral Nutrition

• For continuous tube feeding, calculate nutritional insulin as 1 unit per 10-15 grams of carbohydrate per day 1
• For patients not previously on insulin, start with 5 units of NPH/detemir every 12 hours or 10 units of glargine every 24 hours 1, 2
• For bolus enteral feedings, give 1 unit of regular or rapid-acting insulin per 10-15 grams of carbohydrate before each feeding 1

Glucocorticoid Therapy

• For patients on once-daily morning steroids, use prandial insulin (often NPH) to cover daytime hyperglycemia 1
• For long-acting glucocorticoids or continuous use, add 0.1-0.3 units/kg/day of glargine to the usual regimen 2

Critical Pitfalls to Avoid

• Never use sliding-scale insulin alone in hospitalized patients with known diabetes 1
• Do not continue escalating basal insulin beyond 0.5-1.0 units/kg/day without addressing postprandial hyperglycemia with prandial insulin 2
• Avoid intramuscular injections, especially with long-acting insulins, as severe hypoglycemia may result 1
• Do not inject into areas of lipodystrophy or localized cutaneous amyloidosis, as this causes erratic absorption 1, 3
• Do not dilute or mix insulin glargine with any other insulin or solution 2, 3
• Do not administer insulin glargine intravenously or via an insulin pump 3
• Recognize that 75% of hypoglycemic episodes occur in patients using basal insulin, with peak incidence between midnight and 6:00 AM 1

Administration Technique

• Inject subcutaneously into the abdominal area, thigh, or deltoid 3
• Rotate injection sites within the same region to reduce lipodystrophy risk 3
• Use the shortest needles (4-mm pen or 6-mm syringe needles) as first-line choice—they are safe, effective, and less painful 5
• Visually inspect insulin for particulate matter and discoloration before administration 3