What types of insulin are recommended for a patient with diabetes, considering factors such as severity of condition, lifestyle, and other health considerations?

Types of Insulin for Diabetes Management

Insulin Classification by Duration of Action

Insulin therapy should be selected based on diabetes type, with rapid-acting and long-acting insulins forming the foundation of modern physiologic replacement regimens. 1, 2

Rapid-Acting Insulin Analogues

• Insulin lispro is administered 0-15 minutes before meals to control postprandial glucose excursions 3, 4, 2
• Rapid-acting analogues provide better postprandial glucose control than regular insulin with less delayed hypoglycemia 2, 5
• These insulins are essential components of basal-bolus regimens in both type 1 and type 2 diabetes 3, 4

Short-Acting (Regular) Insulin

• Regular human insulin requires administration 30-45 minutes before meals 4
• Less commonly used now due to inferior postprandial control compared to rapid-acting analogues 2

Intermediate-Acting Insulin

• NPH (Neutral Protamine Hagedorn) insulin is typically administered once or twice daily as basal coverage 4, 2
• For patients on enteral/parenteral feeding, 5 units of NPH every 12 hours represents a reasonable starting point 1

Long-Acting Basal Insulin Analogues

• Insulin glargine (Lantus) provides 24-hour basal coverage with once-daily dosing at 10 units or 0.1-0.2 units/kg/day for insulin-naive type 2 diabetes patients 1, 2
• Insulin degludec is an ultra-long-acting basal insulin offering greater flexibility in administration timing with reduced hypoglycemia risk compared to glargine 6, 7
• Long-acting analogues more closely mimic physiologic basal insulin needs than NPH 7, 5

Premixed Insulin Formulations

• Premixed insulins combine intermediate-acting and short/rapid-acting components in fixed ratios 2, 8
• Two or three premixed insulin injections per day may be used in type 1 diabetes, though this approach offers less flexibility 2
• Premixed insulin should be avoided in hospitalized patients due to unacceptably high rates of iatrogenic hypoglycemia 1

Insulin Selection by Diabetes Type

Type 1 Diabetes

• Multiple daily injections with basal-bolus therapy is the standard approach, providing approximately 50% of total daily dose as basal insulin and 50% as prandial insulin 1, 2, 5
• Total daily insulin requirements typically range from 0.4-1.0 units/kg/day, with 0.5 units/kg/day being typical for metabolically stable patients 1
• Rapid-acting insulin analogues (lispro) are given 0-15 minutes before meals combined with once-daily long-acting basal insulin (glargine or degludec) 3, 2

Type 2 Diabetes

• Begin with basal insulin alone (10 units once daily or 0.1-0.2 units/kg/day) in combination with metformin 9, 1
• When A1C ≥9% or blood glucose ≥300-350 mg/dL with symptomatic/catabolic features, initiate basal-bolus insulin immediately rather than basal insulin alone 9, 1
• Add prandial insulin when basal insulin exceeds 0.5 units/kg/day or when fasting glucose reaches target but A1C remains elevated after 3-6 months 9, 1

Critical Dosing Thresholds and Titration

Initial Dosing

• Type 2 diabetes: Start with 10 units once daily or 0.1-0.2 units/kg/day of basal insulin 1
• Type 1 diabetes: Start with 0.5 units/kg/day total daily dose, split 50% basal and 50% prandial 1
• Severe hyperglycemia (A1C ≥10%): Consider 0.3-0.5 units/kg/day as total daily dose 9, 1

Titration Algorithm

• Increase basal insulin by 2 units every 3 days if fasting glucose is 140-179 mg/dL 1
• Increase basal insulin by 4 units every 3 days if fasting glucose ≥180 mg/dL 1
• Target fasting plasma glucose: 80-130 mg/dL 9, 1

Critical Threshold: Preventing Overbasalization

• When basal insulin exceeds 0.5 units/kg/day, add prandial insulin rather than continuing to escalate basal insulin alone 9, 1
• Clinical signals of overbasalization include bedtime-to-morning glucose differential ≥50 mg/dL, hypoglycemia, and high glucose variability 1

Special Considerations

Insulin Delivery Methods

• Continuous subcutaneous insulin infusion (pump therapy) provides approximately 40-60% of total daily dose as basal delivery 1, 4
• The shortest needles (4-mm pen and 6-mm syringe needles) are safest, most effective, and should be first-line choice in all patients 2
• Intramuscular injections must be avoided, especially with long-acting insulins, as severe hypoglycemia may result 2

Combination Therapy

• Metformin should be continued when adding or intensifying insulin therapy unless contraindicated 9, 1, 2
• Metformin combined with insulin reduces weight gain, lowers insulin dose requirements, and decreases hypoglycemia compared to insulin alone 2
• GLP-1 receptor agonists can be added to basal insulin to address postprandial hyperglycemia while minimizing weight gain and hypoglycemia risk 9, 1

High-Risk Populations

• Elderly patients (>65 years), those with renal failure, or poor oral intake require lower doses (0.1-0.25 units/kg/day) 1
• Hospitalized patients on high-dose home insulin (≥0.6 units/kg/day) should have total daily dose reduced by 20% upon admission 1, 6

Common Pitfalls to Avoid

• Never delay insulin initiation in patients not achieving glycemic goals with oral medications 1
• Never continue escalating basal insulin beyond 0.5-1.0 units/kg/day without addressing postprandial hyperglycemia 1
• Never use sliding scale insulin as monotherapy—it is explicitly condemned by all major diabetes guidelines 1
• Never abruptly discontinue oral medications when starting insulin therapy due to risk of rebound hyperglycemia 2
• Never inject into areas of lipohypertrophy, as this distorts insulin absorption 2