Types of Fast- and Short-Acting Insulins

What Are Bolus Insulins and What Kinds Are Available?

Preparing fast-acting insulin. Digital Vision/Getty Images

When it comes to taking insulin, there are several types, including fast-acting, short-acting, intermediate-acting and long-acting. This article helps you distinguish between the main types of fast- and short-acting insulins.

Read more: Understanding Basal and Bolus Insulins

Who Needs to Take Insulin

All people with type 1 diabetes, and some people with type 2 diabetes, need to take insulin in order to process the glucose from food.

In type 1 diabetes, this is because the pancreas no longer makes insulin. In type 2 diabetes, the pancreas makes insulin, but their bodies no longer respond as well to it, sometimes making injections of insulin necessary.

What Is Bolus Insulin?

Bolus insulin refers to the extra amounts of insulin the pancreas would naturally make in response to glucose taken in through food. The amount of bolus insulin produced depends on the size of the meal.

In the person with type 1 diabetes, the pancreas no longer automatically makes insulin regardless of the intake of glucose.

The beta cells that produce the insulin have largely shut down. Both the basal, or long-term background insulin, and the bolus, or quick bursts of insulin needed at mealtimes, must be obtained through injections or an insulin pump in order to process all of the glucose taken in through food or released by the liver.

Types of Bolus Insulins

Fast- and short-acting insulins are primarily used to balance glucose levels at mealtimes (called a bolus dose).

 A person with type 1 diabetes typically has to take multiple injections of a bolus insulin each day to cover their meals and snacks, along with a basal dose to keep the background insulin in check.

There are two types of bolus insulins: rapid-acting (also known as fast-acting) and short-acting insulins (also known as regular insulin).

In 2015, another type of rapid-acting insulin became available in the U.S. It's an inhaled insulin by the brand name Afrezza.

The main differences between these types of insulin is how quickly they reach your bloodstream and begin to reduce your blood sugar (onset), when the insulin begins to work the hardest (peak action), and how long they last for (duration). 

Fast-acting bolus insulins, such as NovoLog, Apidra and Humalog begin to start lowering your blood glucose within 5 - 15 minutes. Short-acting insulins (Regular) have an onset of about 30 minutes. Each of these bolus insulins are designed to be taken just before a meal and have a duration of up to five hours for NovoLog, Apidra, and Humalog, and seven hours for Regular.

Fast-Acting Insulins

There are currently three fast-acting insulins

1. Brand name: Novolog (generic name: aspart):

  • Onset: 5-15 minutes
  • Peak action: 1-3 hours
  • Duration: 3-5 hours

2. Brand name: Apidra (generic name: glulisine):

  • Onset: 5-15 minutes
  • Peak action: 30 minutes-90 minutes
  • Duration: 3-5 hours

3. Brand name: Humalog (generic name: lispro):

  • Onset: 5-15 minutes
  • Peak action: 30 minutes-90 minutes
  • Duration: 3-5 hours

Short-Acting Insulin

There are currently two short-acting insulins available.

Both go by the generic name "regular" and are displayed as (R).

1. Brand name: Humulin (R):

  • Onset: 5-15 minutes
  • Peak action: 2-4 hours
  • Duration: 5-8 hours

2. Brand name: Novolin (R):

  • Onset: 5-15 minutes
  • Peak action: 2-4 hours
  • Duration: 5-8 hours


Insulin. American Diabetes Association. " Consumer’s Guide 2011. " Diabetes Forecast, January 2011, Vol, 64, No. 1.

Hieronymus, L. M.S.Ed., A.P.R.N., B.C.-A.D.M., C.D.E., Geil, P. M.S., R.D., C.D.E. "Types of Insulin. " Diabetes Self-Management, 2009.

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