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 optimize glycemic control. 1

Classification of Insulin Types

Rapid-Acting Insulins

• Examples: Insulin lispro, insulin aspart, insulin glulisine
• Onset: 5-15 minutes
• Peak: 1-2 hours
• Duration: 3-5 hours
• Clinical use: Administered just before meals to control postprandial glucose excursions
• Appearance: Clear solution
• Special characteristics:
  • Insulin glulisine is produced by recombinant DNA technology using E. coli K12 2
  • Can be administered immediately before meals, offering greater flexibility 3
  • Lower risk of postprandial hypoglycemia compared to regular insulin 4

Short-Acting Insulins

• Example: Regular insulin
• Onset: 30 minutes
• Peak: 2-3 hours
• Duration: 6-8 hours
• Clinical use: Administered 30-45 minutes before meals
• Appearance: Clear solution
• Special characteristics:
  • Longer duration increases risk of postprandial hypoglycemia 4
  • Should be injected 30-45 minutes before meals for optimal effect 5

Intermediate-Acting Insulins

• Examples: NPH (Neutral Protamine Hagedorn), Lente
• Onset: 1-2 hours
• Peak: 6-8 hours
• Duration: 12-18 hours
• Clinical use: Provides basal insulin coverage
• Appearance: Uniformly cloudy
• Special characteristics:
  • Contains protamine which delays absorption
  • Has pronounced peak effect, increasing risk of nocturnal hypoglycemia 4

Long-Acting Insulins

• Examples: Insulin glargine, insulin detemir, insulin degludec, Ultralente
• Onset: 1-2 hours
• Peak: Minimal to none
• Duration: 20-42+ hours
• Clinical use: Provides basal insulin coverage with less risk of hypoglycemia
• Appearance: Insulin glargine is clear; others may be cloudy
• Special characteristics:
  • More constant effect lasting at least 24 hours 6
  • Lower risk of nocturnal hypoglycemia compared to NPH 3, 7
  • Insulin glargine should not be mixed with other insulins due to its acidic pH 1

Premixed Insulin Formulations

• Examples: 70% NPH/30% regular, 75% NPL/25% insulin lispro, 50% NPH/50% regular
• Clinical use: Convenient option for patients requiring both basal and prandial coverage
• Special characteristics:
  • Reduces number of daily injections 7
  • NPL (Neutral Protamine Lispro) was developed specifically to be mixed with insulin lispro 5
  • Premixed insulin lispro can be injected just before meals, unlike human insulin mixtures which require 30-45 minute lead time 5

Important Considerations for Insulin Use

Storage

• Unopened insulin vials should be refrigerated (36-46°F or 2-8°C)
• Avoid extreme temperatures (<36°F or >86°F) to prevent loss of potency
• Insulin in use may be kept at room temperature to reduce injection site irritation
• Opened vials should be discarded after 28 days, even if insulin remains 1, 8

Visual Inspection

• Rapid-acting and short-acting insulins should appear clear
• Intermediate and most long-acting insulins should appear uniformly cloudy
• Check for clumping, frosting, precipitation, or changes in clarity/color before use 1

Mixing Guidelines

• Insulin glargine should not be mixed with other insulins due to its acidic pH
• NPH insulin should not be mixed with lente insulins (zinc phosphate may precipitate)
• When mixing rapid-acting insulin with intermediate or long-acting insulin, inject within 15 minutes before a meal
• Commercially available premixed insulins may be used if the ratio is appropriate for the patient's needs 1

Clinical Advantages of Insulin Analogs

• Rapid-acting analogs provide better postprandial glucose control than regular human insulin 6, 7
• Long-acting analogs have flatter activity profiles with lower risk of hypoglycemia 7
• Insulin detemir is associated with less weight gain compared to NPH insulin 7
• Insulin analogs offer greater flexibility and convenience for patients 7

Pitfalls and Caveats

• Pharmacists and healthcare providers should not interchange insulin species or types without prescriber approval and patient notification
• When purchasing insulin, patients should verify the type and check the expiration date
• Changing insulin types should always be done under medical supervision
• Patients should always have a spare vial of each type of insulin used
• Insulin potency may decrease after the bottle has been in use for more than one month, especially if stored at room temperature 1