What are the different types of insulin?

Types of Insulin

Insulin is available in rapid-acting, short-acting, intermediate-acting, and long-acting types that can be injected separately or mixed in the same syringe to provide optimal glycemic control for patients with diabetes. 1

Classification of Insulin Types

Rapid-Acting Insulins

• Examples: Insulin lispro, insulin aspart, insulin glulisine 1, 2
• Onset: 15-30 minutes
• Peak Action: 1-3 hours
• Duration: 3-5 hours
• Appearance: Clear solution 1
• Clinical Use: Administered immediately before meals to control postprandial glucose excursions 2

Short-Acting Insulins

• Example: Regular insulin (Humulin R) 1
• Onset: 30-60 minutes
• Peak Action: 2-4 hours
• Duration: 5-8 hours
• Appearance: Clear solution 1
• Clinical Use: Administered 30 minutes before meals

Intermediate-Acting Insulins

• Examples: NPH (Neutral Protamine Hagedorn), Lente 1
• Onset: 2-4 hours
• Peak Action: 4-12 hours
• Duration: 12-18 hours
• Appearance: Uniformly cloudy suspension 1
• Clinical Use: Provides basal insulin coverage

Long-Acting Insulins

• Examples: Insulin glargine, insulin detemir, insulin degludec 1, 2
• Onset: 1-2 hours
• Peak Action: Minimal peak (relatively flat profile)
• Duration: 20-24+ hours
• Appearance: Clear solution (glargine) 1
• Clinical Use: Provides steady background insulin coverage with less risk of nocturnal hypoglycemia 2

Premixed Insulin Formulations

Premixed insulins combine fixed ratios of intermediate-acting insulin with short or rapid-acting insulin:

• 70% NPH/30% regular
• 50% NPH/50% regular
• 75% NPL/25% insulin lispro 1

These formulations offer convenience for patients who have difficulty mixing insulins or who need simplified regimens.

Source and Manufacturing

Modern insulins are produced through several methods:

• Recombinant DNA technology: Most common method for human insulin production using bacteria or yeast 1
• Animal-derived: Historically obtained from pork pancreas, less commonly used today 1
• Insulin analogs: Created by modifying the amino acid sequence of the insulin molecule to alter pharmacokinetic properties 1

Clinical Considerations

Storage Requirements

• Unopened insulin should be refrigerated (36-46°F/2-8°C) 3
• Insulin in use can be kept at room temperature (below 86°F/30°C) for limited periods:
  • Most insulins: 28 days
  • Insulin in pumps: 19 days 4
• Avoid freezing or exposure to extreme heat or direct sunlight 3

Visual Inspection

• Rapid-acting and short-acting insulins should appear clear
• Intermediate and premixed insulins should appear uniformly cloudy
• Inspect for clumping, frosting, precipitation, or color changes before use 1

Mixing Guidelines

• Insulin glargine should not be mixed with other insulins due to its acidic pH 1
• NPH can be mixed with rapid or short-acting insulins 1
• Phosphate-buffered insulins (e.g., NPH) should not be mixed with lente insulins 1

Modern Insulin Therapy Approaches

Basal-Bolus Therapy

This approach most closely mimics physiological insulin secretion:

• Basal component: Long-acting insulin provides background insulin coverage
• Bolus component: Rapid-acting insulin at mealtimes addresses postprandial glucose excursions 2, 5

Benefits of Newer Insulin Analogs

• Faster onset of action for rapid-acting analogs
• More predictable absorption
• Lower risk of hypoglycemia, especially nocturnal hypoglycemia
• Less day-to-day variability in glucose control 2, 6

Common Pitfalls and Caveats

1. Insulin substitution risks: Changes in insulin type, brand, or species should be made cautiously and only under medical supervision, as dosage adjustments may be required 3

2. Visual inspection importance: Always inspect insulin before use; cloudy insulins that appear clear or clear insulins that appear cloudy may indicate loss of potency 1

3. Mixing incompatibilities: Some insulins cannot be mixed (e.g., insulin glargine with other insulins) 1

4. Storage errors: Improper storage can lead to loss of potency; never use insulin that has been frozen or exposed to extreme heat 3

5. Confusing insulin types: Mistaking rapid-acting for long-acting insulin (or vice versa) can lead to dangerous dosing errors 2

By understanding the different types of insulin and their properties, healthcare providers can select appropriate insulin regimens that optimize glycemic control while minimizing the risk of hypoglycemia and other complications.