Short-Acting Insulin vs. Rapid-Acting Insulin
| Author: Judy Kohn, RN, BSN, CDE |
| Last Updated: Friday, December 28, 2007 |
Q: “I was taking regular insulin before each meal and NPH at bed. My doctor recently switched my NPH to Lantus®, and kept the regular insulin the same. I met someone in a diabetes class who is on a similar routine but uses Humalog® instead of the regular insulin before each meal, and her doctor said the Humalog is better. What’s the difference between regular insulin and Humalog?"
A: First of all, there are many different insulins as well as different insulin regimens, because each person with diabetes may have not only individual needs but also a varied response to an insulin regimen. After you read this answer, be sure to discuss this with your diabetes team.
Regular insulin is the original and only insulin that is called a short-acting insulin, while Humalog (as well as NovoLog® and Apidra®) is a rapid-acting insulin. For simplicity in this answer, I will refer to them as short-acting vs. rapid-acting insulins.
Short-Acting Insulin
Short-acting insulin has these characteristics:
- It has an onset of action of approximately 30 to 60 minutes after injection, a peak action from 2 to 3 hours after injection, and a duration of effectiveness of 3 to 6 hours.
- Ideally, you are supposed to inject this insulin at least ½ to 1hour before eating to get the best benefit.
- The action of this insulin is dosage dependent, meaning that the more you take, the longer it lasts—and in fact, this insulin can last up to 16 hours, depending on the dose, site of injection, and individual variability.
- Short-acting insulin does not mimic the normal pancreas, partly because most people do not allow adequate time between the injection and the meal. As a result, generally you might observe that the insulin does not peak quickly enough to control your post-meal glucose, yet it can peak late or have a duration later than expected, resulting sometimes in a high blood glucose 1-2 hours after the meal followed by a low glucose before the next meal.
- This type of insulin is not as convenient if you dine out frequently, since it is risky to take insulin before you get to the restaurant when you are not sure when you will get to eat or what you will eat; however, that means that often you may be injecting very soon before you eat, with the result that your post-meal glucose may rise too high because the insulin has not had time to begin working.
- However, it is always important to note that each person is different and this insulin works fine for some people. Also, it costs less than the rapid-acting insulins.
Rapid-Acting Insulin
Rapid-acting insulins are actually called insulin analogues because they were synthetically developed using recombinant DNA technology to improve the absorption and activity profiles to better mimic how the normal pancreas works.
Rapid-acting insulins have these characteristics:
- They have an onset of action of approximately 5 to 15 minutes after injection, a peak action of about one hour after injection, and a duration of effectiveness of 3 to 5 hours.
- In general, rapid-acting insulins peak more than two times higher and in less than half the time than does short-acting insulin. As a result, you can eat sooner after injecting rapid-acting insulin, and still have an improved post-meal glucose with a reduced risk of hypoglycemia later on.
- Note however that some people have the misconception that this rapid-acting insulin works “immediately”, and they have gotten lax on heeding the recommendation to allow a little time between the injection and the meal. Recent studies and individual observations have suggested that rapid-acting insulins usually are more effective in controlling the post-meal glucose if you inject the insulin 15 minutes before the meal, rather than immediately before or during the meal.
- Both the action and absorption of rapid-acting insulins are generally more consistent and less affected by injection site.
- While rapid-acting insulin improves the post-meal glucose, your glucose could rise later on if you do not have adequate coverage from your basal insulin (which is the Lantus you are taking).
Which is better? It depends…
You can probably see that based on the characteristics listed, it depends on individual circumstances and needs.
- Short-acting insulin costs less, but it requires that you allow more time between your injection and your meal. It will not bring down a temporary high glucose as fast as would a rapid-acting insulin.
- Rapid-acting insulin costs a little more but provides more flexibility on the timing of the injection while still controlling the post-meal glucose (or bringing down a temporarily elevated glucose). However, because it does not last as long as short-acting insulin, this type of insulin requires adequate basal insulin coverage, which means generally taking a long-acting insulin once or twice a day.
Summing it up:
If you are happy with your current regimen and your glucose readings are mostly within your target range (as is your A1C result), then you may be fine staying with your current regimen.
However, if you are not happy with your current level of glucose control, or if after reading this you realize that your insulin regimen seems too inconvenient for you, then you may want to discuss this with your diabetes team to see if you need an adjustment in your dosage or the types of insulin you use.
Related Questions
Insulin Cocktails
Q:
"Would you explain the term "insulin cocktail" where regular and
Humalog® are mixed to handle unusual BG patterns?"
Related Links
American Diabetes Association
http://www.diabetes.org
Diabetes Self-Management
http://www.diabetesselfmanagement.com
Humalog
http://www.humalog.com
Eli Lilly and Company
http://lillydiabetes.com
Important Notice: The responses provided by the team of Diabetes Educators are based on their personal experiences and expertise as practicing diabetes healthcare professionals, and are not to be considered diabetes management advice from Abbott Laboratories. Remember that information provided by the team of Diabetes Educators is for general background purposes and is not intended as a substitute for medical diagnosis or treatment by a trained professional. You should always consult your physician about any healthcare questions you may have, especially before trying a new medication, diet, fitness program, or approach to healthcare issues.
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