What is the recommended method to determine the total daily dose of insulin?

Determining Total Daily Insulin Dose

For insulin-naive patients with type 2 diabetes, start with 10 units once daily or 0.1-0.2 units/kg body weight; for type 1 diabetes, begin with 0.5 units/kg/day as the total daily dose, split 50% basal and 50% prandial insulin. 1, 2

Type 1 Diabetes: Initial Total Daily Dose Calculation

Weight-based dosing is the standard approach for type 1 diabetes:

• Start with 0.4-1.0 units/kg/day as total daily insulin requirement 1, 2
• For metabolically stable patients, use 0.5 units/kg/day as the typical starting point 1, 2
• Divide this total: approximately 50% as basal insulin and 50% as prandial insulin split among three meals 1, 2

Example calculation for a 70 kg patient with type 1 diabetes:

• Total daily dose = 0.5 units/kg × 70 kg = 35 units/day 2
• Basal insulin (glargine) = 17.5 units once daily 2
• Prandial insulin = 17.5 units divided among meals (approximately 6 units per meal) 2

Higher doses are required in specific situations:

• Immediately following diabetic ketoacidosis presentation 1, 2
• During puberty (often exceeding 1.0 units/kg/day) 1, 2
• During pregnancy and acute medical illness 2

Critical pitfall: Patients in the "honeymoon phase" with residual beta-cell function may require much lower doses of 0.2-0.6 units/kg/day 2

Type 2 Diabetes: Initial Total Daily Dose Calculation

The approach differs based on hyperglycemia severity:

Mild-to-Moderate Hyperglycemia

• Start with 10 units once daily OR 0.1-0.2 units/kg/day of basal insulin 1, 2, 3
• Continue metformin (unless contraindicated) and possibly one additional non-insulin agent 1, 2
• This basal-only approach is appropriate when A1C is <9% 1, 2

Severe Hyperglycemia Requiring Immediate Basal-Bolus

When blood glucose ≥300-350 mg/dL and/or A1C ≥10-12% with symptomatic or catabolic features:

• Start with 0.3-0.5 units/kg/day as total daily dose 2
• Split 50% as basal insulin and 50% as prandial insulin from the outset 1, 2
• This immediate basal-bolus approach prevents prolonged severe hyperglycemia 1, 2

Dose Titration Algorithm

After establishing the initial dose, systematic titration is essential:

Basal Insulin Titration

• Increase by 2 units every 3 days if fasting glucose is 140-179 mg/dL 2
• Increase by 4 units every 3 days if fasting glucose ≥180 mg/dL 2
• Target fasting plasma glucose: 80-130 mg/dL 2
• If hypoglycemia occurs without clear cause, reduce dose by 10-20% immediately 2

Critical Threshold: When to Stop Escalating Basal Insulin

When basal insulin exceeds 0.5 units/kg/day and approaches 1.0 units/kg/day, add prandial insulin rather than continuing to escalate basal insulin alone 1, 2. This prevents "overbasalization," which manifests as:

• Bedtime-to-morning glucose differential ≥50 mg/dL 2
• Hypoglycemia episodes 2
• High glucose variability 2

Adding Prandial Insulin

When basal insulin is optimized but A1C remains above target after 3-6 months:

• Start with 4 units of rapid-acting insulin before the largest meal OR 10% of current basal dose 1, 2
• Titrate prandial insulin by 1-2 units or 10-15% every 3 days based on postprandial glucose 2

Alternative Method: Converting from Current Insulin Regimen

When transitioning to basal-bolus from existing insulin therapy:

• Add up the total current insulin dose 1
• Provide 50% as basal insulin once daily 1
• Provide 50% as prandial insulin, split evenly between three meals 1

When switching from NPH twice daily to glargine once daily:

• Use 80% of the total NPH dose as the starting glargine dose 3

When switching from TOUJEO (insulin glargine 300 units/mL) to standard glargine:

• Use 80% of the TOUJEO dose 3

Special Populations and Situations

Hospitalized Patients

• For insulin-naive or low-dose insulin patients: 0.3-0.5 units/kg/day total, with half as basal 2
• For patients on high-dose home insulin (≥0.6 units/kg/day): reduce total daily dose by 20% to prevent hypoglycemia 2
• For elderly (>65 years), renal failure, or poor oral intake: use lower doses of 0.1-0.25 units/kg/day 2

Enteral/Parenteral Feeding

• Basal insulin needs are typically 30-50% of total daily insulin requirement 2
• Reasonable starting point: 10 units of insulin glargine every 24 hours 2

Essential Monitoring Requirements

Daily fasting blood glucose monitoring is mandatory during titration 2. Equip patients with self-titration algorithms based on self-monitoring of blood glucose, as this approach improves glycemic control 1. Reassess insulin adequacy at every clinical visit, specifically looking for signs of overbasalization 2.

Common Pitfalls to Avoid

Never delay insulin initiation in patients not achieving glycemic goals with oral medications 2. Do not continue escalating basal insulin beyond 0.5-1.0 units/kg/day without addressing postprandial hyperglycemia, as this leads to suboptimal control and increased hypoglycemia risk 2. Always continue metformin when adding or intensifying insulin therapy unless contraindicated 2. Never use sliding scale insulin alone, especially in type 1 diabetes 4.