Insulin, a hormone produced by the pancreas, regulates blood sugar by moving glucose into cells for energy. In diabetes, insufficient insulin or ineffective use leads to high blood sugar. Various insulin therapies exist, each with different action profiles. Intermediate-acting insulin provides a sustained effect over several hours.
Understanding Intermediate-Acting Insulin
Intermediate-acting insulin has a duration of action between faster-acting and longer-acting insulins. Unlike clear rapid or long-acting insulins, it is typically cloudy due to specific chemical modifications that slow its absorption.
NPH (Neutral Protamine Hagedorn) insulin is a common example. In NPH, human insulin is combined with protamine and zinc, forming a suspension. This creates microscopic crystals that dissolve gradually after injection, allowing for prolonged release.
How Intermediate-Acting Insulin Works
Intermediate-acting insulin provides a steady supply of insulin over an extended period. Its action is described by three phases: onset, peak, and duration. Onset is how quickly it begins to lower blood sugar, typically within 1 to 4 hours.
The peak effect, when it works most effectively, generally occurs 4 to 12 hours after injection. Its modified structure allows for gradual absorption, leading to this delayed and prolonged peak. The total duration of its action, how long it continues to lower blood sugar, ranges from 12 to 24 hours.
Its Role in Diabetes Management
Intermediate-acting insulin provides “basal” or background insulin coverage. Basal insulin is the continuous, low-level supply the body needs to regulate glucose production and maintain stable blood sugar between meals and overnight.
It is commonly prescribed once or twice daily. Many individuals use it with rapid-acting insulin, taken before meals to cover glucose from food. This combination therapy aims to mimic the body’s natural insulin release patterns, providing both continuous background control and specific coverage for meals.
Distinguishing It From Other Insulins
Insulin therapies are categorized by onset, peak, and duration. Intermediate-acting insulin holds a unique position.
Rapid-acting insulins work within 15 minutes, peak in 1 hour, and last 2 to 4 hours, primarily for mealtime spikes. Short-acting (regular) insulin has a slower onset (30-60 minutes), peaks around 2-5 hours, and lasts 5-8 hours, also for mealtime glucose but requiring earlier administration.
Long-acting insulins (e.g., glargine, detemir) have a 1-2 hour onset, little to no peak, and provide a steady effect for 24 hours or more, designed for continuous basal coverage.
Intermediate-acting insulin (onset 1-4 hours, peak 4-12 hours, duration 12-24 hours) bridges the gap between faster-acting mealtime insulins and the more prolonged action of long-acting basal insulins. It provides sustained blood sugar control, often complementing mealtime insulins.