How to Start Insulin in Diabetic Patients: Specific Dosing Guidelines
For Type 2 Diabetes: Start with 10 units of basal insulin once daily or 0.1-0.2 units/kg body weight, administered at the same time each day, and titrate by 2-4 units every 3 days until fasting glucose reaches 80-130 mg/dL. 1, 2, 3
Initial Dosing for Type 2 Diabetes
Standard Starting Dose
- Begin with 10 units once daily for most insulin-naive patients with mild-to-moderate hyperglycemia 1, 2, 3
- Alternatively, use 0.1-0.2 units/kg/day based on body weight and degree of hyperglycemia 4, 1, 3
- Administer at the same time every day (any time, but consistency is critical) 1, 3
- Continue metformin unless contraindicated, and possibly one additional non-insulin agent 1, 2
Higher Starting Doses for Severe Hyperglycemia
- For A1C ≥9% or blood glucose ≥300-350 mg/dL: Consider 0.3-0.5 units/kg/day as total daily dose, split between basal and prandial insulin 1, 5
- For A1C ≥10-12% with symptomatic or catabolic features: Start basal-bolus insulin immediately (approximately 50% basal, 50% prandial) 1, 5
Titration Algorithm
Evidence-Based Dose Adjustments
- If fasting glucose 140-179 mg/dL: Increase by 2 units every 3 days 1, 5
- If fasting glucose ≥180 mg/dL: Increase by 4 units every 3 days 1, 5
- Target fasting glucose: 80-130 mg/dL 1, 5
- If hypoglycemia occurs: Reduce dose by 10-20% immediately 1, 5
- If fasting glucose <80 mg/dL on ≥2 occasions per week: Decrease by 2 units 1
Patient Self-Titration
- Equip patients with self-titration algorithms based on self-monitoring of blood glucose to improve glycemic control 1, 2
- Daily fasting blood glucose monitoring is essential during titration 1, 5
Critical Threshold: When to Stop Escalating Basal Insulin
The 0.5 units/kg/day Rule
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, 5
Signs of Overbasalization
- Basal dose >0.5 units/kg/day 1
- Bedtime-to-morning glucose differential ≥50 mg/dL 1
- Hypoglycemia episodes 1
- High glucose variability 1
Adding Prandial Insulin
When to Add Mealtime Coverage
- After 3-6 months of basal insulin optimization, if fasting glucose is controlled (80-130 mg/dL) but A1C remains above target 1, 5
- When basal insulin approaches 0.5-1.0 units/kg/day without achieving glycemic goals 1, 5
- When significant postprandial glucose excursions occur (>180 mg/dL) 1
Starting Prandial Insulin Dose
- Begin with 4 units of rapid-acting insulin before the largest meal 4, 1
- Alternatively, use 10% of the current basal dose 4, 1
- Titrate by 1-2 units or 10-15% every 3 days based on 2-hour postprandial glucose readings 1, 5
Initial Dosing for Type 1 Diabetes
Total Daily Dose Calculation
- Start with 0.5 units/kg/day as total daily insulin for metabolically stable patients 1, 3
- Total daily requirements typically range from 0.4-1.0 units/kg/day 1, 3
- Split 50% as basal insulin (given once daily) and 50% as prandial insulin (divided among three meals) 1, 3
Example for 70 kg Patient
- Total daily dose: 35 units (0.5 × 70 kg)
- Basal insulin (glargine): 17-18 units once daily
- Prandial insulin (rapid-acting): 5-6 units before each meal
Important Note
- Type 1 diabetes patients must use short-acting insulin at mealtimes in addition to basal insulin 3, 6
- Basal insulin alone is insufficient for type 1 diabetes 3, 6
Special Populations Requiring Dose Adjustments
Lower Starting Doses (0.1-0.25 units/kg/day)
- Elderly patients (>65 years) 1
- Renal failure or hepatic impairment 1
- Poor oral intake or acute illness 1
- Thin or normal weight patients 7
- Conditions with high insulin sensitivity (hypothyroidism, adrenal insufficiency) 7
Higher Starting Doses (Add 0.2 units/kg to standard dose)
- Marked obesity with metabolic syndrome 7
- Open wounds or active infections 7
- High insulin resistance states 7
Hospitalized Patients
- For insulin-naive or low-dose patients: Start 0.3-0.5 units/kg/day total daily dose, with half as basal insulin 1
- For patients on high-dose home insulin (≥0.6 units/kg/day): Reduce total daily dose by 20% upon admission to prevent hypoglycemia 1
Common Pitfalls to Avoid
Critical Errors
- Never delay insulin initiation in patients not achieving glycemic goals with oral medications 1, 2
- Never continue escalating basal insulin beyond 0.5-1.0 units/kg/day without addressing postprandial hyperglycemia—this leads to overbasalization with increased hypoglycemia risk 1, 5
- Never use sliding scale insulin as monotherapy—it is explicitly condemned by all major diabetes guidelines and shown to be ineffective 1
- Never abruptly discontinue metformin when starting insulin therapy 6
Administration Errors
- Never dilute or mix insulin glargine with any other insulin or solution due to its low pH 1, 3
- Never administer intravenously or via insulin pump 3
- Rotate injection sites within the same region to prevent lipodystrophy 3, 6
Monitoring Requirements
During Titration Phase
- Daily fasting blood glucose monitoring is essential 1, 5
- Check pre-meal glucose before each meal when on prandial insulin 5
- Check 2-hour postprandial glucose after largest meal to guide prandial insulin adjustments 5
- Assess adequacy of insulin dose at every clinical visit 1
Long-Term Monitoring
- Check A1C every 3 months until target achieved 5
- Reassess and modify therapy every 3-6 months once stable 1
Patient Education Essentials
Critical Teaching Points
- Recognition and treatment of hypoglycemia (treat with 15-20g fast-acting carbohydrate when glucose <70 mg/dL) 5, 6
- Proper insulin injection technique with 90-degree angle for subcutaneous administration 5
- Systematic site rotation within one anatomical area 5, 6
- Self-monitoring of blood glucose technique 2, 5
- "Sick day" management rules (continue insulin even when unable to eat) 5
- Insulin storage and handling 5
- Carry at least 15g of carbohydrate at all times 5
Alternative Approaches
GLP-1 Receptor Agonist Combination
- Consider adding a GLP-1 receptor agonist to basal insulin instead of prandial insulin 4, 1
- This combination provides potent glucose-lowering with less weight gain and hypoglycemia compared to intensified insulin regimens 4, 1