Comprehensive Insulin Regimens for Type 2 Diabetes: A-to-Z Guide with Case Examples

Starting Basal Insulin: The Foundation

For patients with type 2 diabetes inadequately controlled on oral medications, initiate basal insulin at 10 units once daily or 0.1-0.2 units/kg body weight, administered at the same time each day, while continuing metformin. 1, 2, 3

Initial Dosing Algorithm

Standard initiation: Start with 10 units once daily for most patients with mild-to-moderate hyperglycemia 1, 2, 3
Weight-based dosing: Use 0.1-0.2 units/kg/day for more precise dosing 1, 2
Severe hyperglycemia (A1C ≥9% or glucose ≥300-350 mg/dL): Consider higher starting doses of 0.3-0.5 units/kg/day as total daily dose, split between basal and prandial insulin 1, 2, 3
Extreme hyperglycemia (A1C ≥10-12% with symptoms): Start basal-bolus insulin immediately rather than basal alone 1, 2

Basal Insulin Titration Protocol

Increase basal insulin systematically every 3 days based on fasting glucose until target of 80-130 mg/dL is achieved. 1, 2, 3

If fasting glucose ≥180 mg/dL: Increase by 4 units every 3 days 1, 2, 3
If fasting glucose 140-179 mg/dL: Increase by 2 units every 3 days 1, 2, 3
Alternative approach: Increase by 10-15% of current dose once or twice weekly 1, 2, 3
If hypoglycemia occurs: Reduce dose by 10-20% immediately 1, 2, 3
If >2 fasting values per week <80 mg/dL: Decrease by 2 units 2

Critical Threshold: Recognizing Overbasalization

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, 3

Clinical signals of overbasalization include: 2, 3

Basal dose >0.5 units/kg/day
Bedtime-to-morning glucose differential ≥50 mg/dL
Hypoglycemia episodes
High glucose variability
Fasting glucose controlled but A1C remains elevated

Adding Prandial Insulin: Intensification Strategy

Add prandial insulin when basal insulin is optimized (fasting glucose 80-130 mg/dL) but A1C remains above target after 3-6 months, or when basal insulin approaches 0.5-1.0 units/kg/day without achieving A1C goal. 1, 2, 3

Prandial Insulin Initiation

Starting dose: 4 units of rapid-acting insulin before the largest meal, or 10% of current basal dose 1, 2, 3
Titration: Increase by 1-2 units or 10-15% every 3 days based on postprandial glucose readings 1, 2
Rapid-acting options: Lispro, aspart, or glulisine administered 0-15 minutes before meals 1, 4

Basal-Bolus Regimen Construction

For patients requiring full basal-bolus therapy: 1, 2

Total daily dose calculation: Add up current total insulin dose
Distribution: Provide 50% as basal insulin once daily and 50% as prandial insulin split evenly between three meals
Alternative method: For type 1 diabetes or severe type 2 diabetes, use 0.5 units/kg/day as total daily dose, split 50% basal and 50% prandial

Case Example 1: Newly Diagnosed Type 2 Diabetes with Moderate Hyperglycemia

Patient: 58-year-old, 90 kg, A1C 8.5%, fasting glucose 180 mg/dL, on metformin 2000 mg/day

Regimen:

Start insulin glargine 10 units at bedtime (or 0.15 units/kg = 13-14 units) 2, 3
Continue metformin 2000 mg/day 1, 2, 3
Titrate by 2 units every 3 days until fasting glucose 80-130 mg/dL 2, 3
Daily fasting glucose monitoring essential 2, 3
Expected to reach approximately 30-40 units within 4-6 weeks

Case Example 2: Severe Hyperglycemia Requiring Immediate Basal-Bolus

Patient: 65-year-old, 80 kg, A1C 11.5%, fasting glucose 280 mg/dL, random glucose 350 mg/dL, symptomatic with polyuria and weight loss

Regimen:

Total daily dose: 0.4 units/kg/day = 32 units 2, 3
Basal insulin: Insulin glargine 16 units at bedtime (50% of total) 2, 3
Prandial insulin: Insulin lispro 5 units before each meal (breakfast, lunch, dinner) 2, 3
Continue metformin 2000 mg/day 2, 3
Titrate basal by 4 units every 3 days based on fasting glucose 2, 3
Titrate prandial by 1-2 units every 3 days based on postprandial glucose 2, 3

Case Example 3: Basal Insulin Optimization with Persistent Elevated A1C

Patient: 62-year-old, 100 kg, on insulin glargine 50 units at bedtime (0.5 units/kg), metformin 2000 mg/day, fasting glucose 110 mg/dL, A1C 8.2%

Problem: Fasting glucose controlled but A1C elevated—indicates postprandial hyperglycemia 2, 3

Regimen adjustment:

Do NOT increase basal insulin further (already at 0.5 units/kg threshold) 2, 3
Add insulin lispro 5 units before largest meal (or 10% of basal = 5 units) 2, 3
Monitor 2-hour postprandial glucose after that meal 2, 3
Titrate prandial insulin by 1-2 units every 3 days 2, 3
If A1C remains elevated after 3 months, add prandial insulin to second meal 2, 3

Insulin Product Selection

Basal Insulin Options

Long-acting analogs (glargine, detemir, degludec) reduce nocturnal hypoglycemia compared to NPH insulin and are preferred. 1, 3, 5, 6, 7

Insulin glargine (Lantus, Toujeo): Once daily, no pronounced peak, duration 24 hours 1, 8, 5, 6, 7
Insulin detemir (Levemir): Once or twice daily 1
Insulin degludec: Ultra-long acting, may require weekly dose adjustments 1, 2
NPH insulin: Less expensive but higher hypoglycemia risk, requires twice-daily dosing 1, 5, 6

Prandial Insulin Options

Rapid-acting analogs (lispro, aspart, glulisine): Administer 0-15 minutes before meals 1, 4
Regular human insulin: Administer 30 minutes before meals, longer duration 1

Foundation Therapy: Never Abandon Metformin

Continue metformin when initiating or intensifying insulin therapy unless contraindicated, as it reduces weight gain, lowers insulin requirements, and decreases hypoglycemia risk. 1, 2, 3, 4

Metformin should be optimized to at least 2000 mg/day (maximum 2500 mg/day) 2
Provides complementary glucose-lowering effects 2
Reduces total insulin requirements 3, 4

Alternative Intensification: GLP-1 Receptor Agonists

Consider adding a GLP-1 receptor agonist to basal insulin instead of prandial insulin to improve A1C while minimizing weight gain and hypoglycemia. 1, 2, 3

Combination basal insulin + GLP-1 RA provides potent glucose-lowering 2
Less weight gain compared to basal-bolus insulin 2, 3
Lower hypoglycemia risk 2, 3
Cardiovascular and kidney benefits with specific agents 9

Administration Guidelines

Injection Technique

Administer subcutaneously into the abdominal area, thigh, or deltoid at the same time each day, rotating injection sites to prevent lipohypertrophy. 1, 8, 4

Use shortest needles (4-mm pen, 6-mm syringe) to avoid intramuscular injection 4
Do not dilute or mix insulin glargine with other insulins 2, 8, 4
Proper site rotation prevents lipohypertrophy and erratic absorption 8, 4

Timing Considerations

Basal insulin: Can be given at bedtime, morning, or any convenient time, but must be consistent 2, 3, 5
Prandial insulin: Administer 0-15 minutes before meals 1, 4
Twice-daily basal dosing: Consider if inadequate 24-hour coverage with once-daily dosing 2, 5

Essential Patient Education

Comprehensive education is mandatory before initiating insulin therapy and includes the following components: 2, 3

Blood glucose self-monitoring: Daily fasting glucose during titration 2, 3
Hypoglycemia recognition and treatment: Symptoms, glucose <70 mg/dL, treatment with 15g carbohydrates 2, 3
Injection technique and site rotation: Proper technique prevents lipohypertrophy 2, 3, 4
Insulin storage and handling: Refrigerate unopened vials, room temperature for 28 days once opened 2, 3
"Sick day" management rules: Never stop insulin, monitor glucose more frequently 2, 3
Nutrition management: Carbohydrate counting for prandial insulin dosing 2, 3

Monitoring Requirements

During Titration Phase

Daily fasting blood glucose monitoring essential 1, 2, 3
Assess insulin dose adequacy at every clinical visit 2, 3
Check A1C every 3 months during intensive titration 2
Look for signs of overbasalization at each visit 2, 3

Long-Term Monitoring

A1C every 3-6 months once stable 1, 2
Reassess and modify therapy every 3-6 months to avoid therapeutic inertia 2
Monitor for hypoglycemia patterns 2, 3
Assess weight changes and adjust insulin accordingly 2

Special Populations

Hospitalized Patients

For hospitalized insulin-naive patients, start with 0.3-0.5 units/kg/day total daily dose, giving 50% as basal insulin and 50% as rapid-acting insulin before meals. 2, 3

Use lower doses (0.1-0.25 units/kg/day) for high-risk patients: elderly (>65 years), renal failure, poor oral intake 2
For patients on high-dose home insulin (≥0.6 units/kg/day), reduce total daily dose by 20% upon hospitalization 2, 3
Avoid premixed insulin in hospital settings due to high hypoglycemia rates 2

Patients on Corticosteroids

For patients without diabetes on steroids: Single morning dose of NPH may be appropriate 2
For patients with diabetes on steroids: Add 0.1-0.3 units/kg/day glargine to usual regimen 2

Common Pitfalls to Avoid

Clinical Inertia

Do not delay insulin initiation in patients failing to achieve glycemic goals on oral medications—this is harmful. 2, 3

Never use insulin as a threat or describe it as punishment 1, 3
Explain the progressive nature of type 2 diabetes objectively 1, 3
Early insulin introduction is encouraged when oral agents fail 6

Overbasalization

Do not continue escalating basal insulin beyond 0.5-1.0 units/kg/day without addressing postprandial hyperglycemia—this leads to suboptimal control and increased hypoglycemia risk. 2, 3

Recognize that blood glucose in the 200s mg/dL reflects both inadequate basal coverage AND postprandial excursions requiring mealtime insulin 2
Do not increase basal insulin to address post-lunch or post-dinner hyperglycemia 2

Medication Management Errors

Do not abruptly discontinue oral medications when starting insulin—risk of rebound hyperglycemia 4
Sulfonylureas, DPP-4 inhibitors, and GLP-1 receptor agonists typically stopped once complex insulin regimens beyond basal are used 1
Continue metformin and SGLT2 inhibitors even with intensive insulin therapy 1, 2

Dosing Errors

Do not wait longer than 3 days between basal insulin adjustments in stable patients 2
Do not recalculate total daily dose daily—prandial doses should be based on carbohydrate-to-insulin ratios and insulin sensitivity factors 2
Always reduce dose by 10-20% immediately if hypoglycemia occurs 2, 3

Case Example 4: Transitioning from Basal-Only to Basal-Bolus

Patient: 70-year-old, 85 kg, on insulin glargine 60 units at bedtime (0.7 units/kg), metformin 2000 mg/day, fasting glucose 120 mg/dL, bedtime glucose 240 mg/dL, A1C 9.2%

Analysis: Overbasalization—basal dose >0.5 units/kg, fasting controlled but A1C elevated, large bedtime-to-morning differential 2, 3