What is Insulin NPH (Neutral Protamine Hagedorn insulin)?

What is Insulin NPH (Neutral Protamine Hagedorn Insulin)?

Insulin NPH is an intermediate-acting basal insulin formulation that provides relatively uniform insulin coverage throughout the day and night, primarily controlling blood glucose by suppressing hepatic glucose production between meals and during sleep. 1

Characteristics of NPH Insulin

• Composition: NPH insulin is a suspension of insulin with protamine and zinc, creating a crystalline structure that delays absorption
• Onset of action: Approximately 1-2 hours after injection
• Peak action: 6-8 hours after administration
• Duration of action: Approximately 12 hours 1
• Administration: Typically given once or twice daily as part of a basal-bolus insulin regimen

Clinical Role in Diabetes Management

NPH insulin serves as a basal insulin option in diabetes management:

• In Type 1 diabetes: Used as the basal component in a basal-bolus regimen, often combined with rapid-acting or short-acting insulin for meal coverage 1
• In Type 2 diabetes: Often added when oral medications are insufficient to control blood glucose levels 1

Comparison with Other Basal Insulins

When compared to newer long-acting insulin analogs (glargine, detemir, degludec):

• Advantages of NPH:

  • Lower cost (significantly more affordable than analog insulins) 1
  • Established efficacy in glycemic control 2

• Disadvantages of NPH:

  • Higher risk of nocturnal hypoglycemia due to its peak action profile 1
  • More variable absorption compared to insulin analogs 3
  • Requires resuspension before injection (must be gently rolled, not shaken)
  • May require twice-daily dosing for optimal coverage 1

Practical Considerations

• Dosing: Typically initiated at 10 units or 0.1-0.2 units/kg of body weight 1
• Storage: Unopened vials should be refrigerated; in-use vials may be kept at room temperature 1
• Administration technique: Requires proper resuspension before injection to ensure accurate dosing
• Monitoring: Regular blood glucose monitoring is essential, particularly during the peak action period (6-8 hours post-injection) to detect potential hypoglycemia

Clinical Pearls

• NPH insulin can be mixed in the same syringe with regular insulin for convenience but should not be mixed with rapid-acting insulin analogs 1
• When transitioning from NPH to long-acting analogs, dose adjustments may be needed as NPH often requires higher total daily doses than some analogs 1
• For patients with cost concerns, NPH remains a viable alternative to more expensive insulin analogs, though with careful attention to the timing of administration to minimize hypoglycemia risk 1

Common Pitfalls

• Failure to properly resuspend NPH insulin before injection can lead to dosing inaccuracies
• Not accounting for the peak action when planning meals and physical activity
• Using the same dosing schedule as long-acting analogs without considering NPH's different pharmacokinetic profile

Despite the availability of newer insulin analogs with flatter action profiles, NPH insulin continues to be an important treatment option, particularly in resource-limited settings or for patients facing cost barriers to newer insulin formulations.