Types of Insulin and Their Uses in Diabetes Management
Insulin therapy is essential for all patients with type 1 diabetes and often necessary for patients with type 2 diabetes when other medications fail to achieve glycemic targets, with specific insulin types selected based on onset, peak, and duration of action to match physiologic needs. 1
Classification of Insulin Types
Basal (Long-Acting) Insulins
Long-acting analogs: Glargine (U100, U300), Detemir, Degludec (U100, U200)
Intermediate-acting: NPH (Neutral Protamine Hagedorn)
Bolus (Mealtime) Insulins
Rapid-acting analogs: Lispro, Aspart, Glulisine
Short-acting: Regular human insulin
- Onset: 30 minutes
- Peak: 2-3 hours
- Duration: 5-8 hours
- Less costly than rapid-acting analogs but with slower onset 2
Premixed Insulins
- Fixed combinations of intermediate-acting and short/rapid-acting insulins
- Examples: 70/30 (70% NPH, 30% Regular) 3
- Advantages: Fewer injections, simplified regimen
- Disadvantages: Less flexibility, requires fixed meal schedule 2, 1
Concentrated Insulins
- U-500 Regular: 5 times more concentrated than U-100
- U-300 Glargine and U-200 Degludec: Higher concentration versions
- Indicated for patients requiring large insulin doses (>200 units/day) 2
- Reduces injection volume for large doses 1
Inhaled Insulin
- Available for prandial use with limited dosing range
- Contraindicated in patients with chronic lung disease
- Not recommended for smokers 2
Insulin Regimens
For Type 1 Diabetes
- Multiple daily injections at diagnosis is typical
- Basal-bolus regimen: Long-acting insulin once/twice daily plus rapid-acting insulin before meals
- Total daily requirements: 0.4-1.0 units/kg/day
- Distribution: 50% basal, 50% prandial 1, 4
For Type 2 Diabetes
- Indications: Acute illness, surgery, pregnancy, glucose toxicity, failure of oral medications, HbA1c ≥10% 4
- Starting approach: Begin with basal insulin (0.1-0.2 units/kg/day) 2, 1
- Intensification options:
- Add mealtime insulin before largest meal
- Add GLP-1 receptor agonist
- Switch to twice-daily premixed insulin 1
Insulin Administration and Dosing
Initiation Dosing
- Basal insulin: 10 units or 0.1-0.2 units/kg/day 2, 1
- Titration: Increase by 10-15% or 2-4 units once or twice weekly until target fasting glucose is achieved 2
- Mealtime insulin: Start with 4 units per meal or 10% of basal dose 2
Mixing Insulins
- Rapid-acting insulin can be mixed with NPH
- Insulin glargine should NOT be mixed with other insulins due to its acidic pH 1
- NPH and short-acting formulations can be mixed and used immediately or stored 1
Administration Technique
- Use shortest needles (4-mm pen, 6-mm syringe) for less pain
- Avoid intramuscular injections to prevent severe hypoglycemia
- Rotate injection sites to prevent lipohypertrophy 4
- Store unopened insulin in refrigerator (36-46°F)
- Current-use insulin should be kept at room temperature (below 86°F) 3
Monitoring and Adjustments
- Monitor blood glucose regularly (4+ tests daily for optimal control)
- Use fasting glucose to titrate basal insulin
- Use both fasting and postprandial glucose to titrate mealtime insulin 1, 4
- Adjust systematically: first fasting, then preprandial, finally postprandial glucose levels 5
Special Considerations
- Elderly patients may require lower doses to reduce hypoglycemia risk 1
- Patients with pre-meal hyperglycemia (>180 mg/dL) benefit from injecting rapid-acting insulin 15 minutes before meals 1
- For frequent hypoglycemia, consider reducing basal dose by 10-20% 1
- Metformin combined with insulin decreases weight gain, lowers insulin dose, and reduces hypoglycemia 4
- Never abruptly discontinue oral medications when starting insulin due to risk of rebound hyperglycemia 4
By understanding the different types of insulin and their appropriate uses, healthcare providers can optimize diabetes management and improve patient outcomes through properly tailored insulin regimens.