Insulin Onset, Peak, and Duration

Insulin Pharmacology

There are several types of insulin commonly used in hospitals, and providers should be aware of their onsets, peaks, and durations.

Insulin is a hormone made by the pancreas that allows the body to use sugar. The green dots represent insulin and the purple dots are sugar.

Insulin Onset, Peak, and Duration

The three relevant terms providers must know concerning insulin are onset, peak, and duration.

• Onset is when the insulin starts working.
• The peak is when the insulin is countering hyperglycemia at its highest level.
• The duration is how long the insulin lasts. The duration ends when all insulin is out of the patient’s system.

Rapid-acting Insulin

The most common rapid-acting insulins are lispro and aspart. Lispro’s brand name is Humalog, and aspart’s is Novolog. Rapid-acting insulins end in “-log.” When a provider monitors a patient’s blood sugar, they will order it before meals (a.c.) or every six hours.

Rapid-acting insulins, such as the industry-standard Novolog, begin working within 30 minutes of administration, so providers should schedule their dosages accordingly. For example, a provider can’t give a patient a rapid-acting insulin one hour before lunch because their insulin levels would be peaking.

Rapid-acting insulin works quickly. It is a mealtime insulin.

The metrics for rapid-acting insulin:

• The onset is within 30 minutes.
• The peak is around one to two hours.
• The duration is about three to five hours.
• Administered 15 minutes before a meal.

These numbers are generalizations, and each patient’s responses are different.

The peak is the most important factor, and providers should ensure their patient receives food before the insulin reaches its peak.

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Short-acting Insulin

Short-acting insulin is known as regular insulin, or Novolin R. It’s still in use, but many hospitals have switched to rapid-acting insulin.

Short-acting insulin’s onset is within an hour. Some may work within 30 minutes, but all provide results within one hour of administration. The insulin peaks within three hours, and its duration is around eight hours. 

The metrics for short-acting insulin:

• The onset is 30 minutes to one hour.
• The peak is around three hours.
• The duration is about eight hours.
• Administered 30 minutes before a meal.

Intermediate-acting Insulin

Intermediate-acting insulins, such as NPH, have an onset between one and two hours. They peak around 10 hours but can be anywhere from 8 to 14 hours. Their duration is about 18 hours.

The metrics for intermediate-acting insulin:

• The onset is 1–2 hours.
• The peak is around 10 hours.
• The duration is about 18 hours.
• This insulin is usually dosed twice daily, often combined with rapid or short-acting insulin.

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Long-acting Insulin

Long-acting insulins include Levemir and glargine, otherwise known as Lantus. Clinicians administer long-acting insulins at night to protect patients from overnight hyperglycemia.

Basal insulin is long-acting. It keeps blood glucose levels stable during periods of fasting, such as overnight.

Both Levemir and Lantus have an onset of 1–2 hours. However, Levemir peaks around eight hours, and the peak is flattened. Lantus does not peak. The duration for both is around 24 hours. 

The metrics for long-acting insulin:

• The onset is 1–2 hours.
• The flattened peak for Levemir is around 8 hours; there is no peak for Lantus.
• The duration is about 24 hours.
• This insulin is usually given once or twice daily. It is a basal insulin, so it is not given in anticipation of food.

Providers need to remember the different types of insulin: rapid-acting, short-acting, intermediate-acting, and long-acting. They all have different onset, peaks, and durations, and it is paramount to understand the different peaks.