Normal bolus! Extended bolus! Square-wave bolus! Combination bolus! Dual-wave bolus!
Whether you are new to pump therapy or an experienced pumper, you’ve probably heard these terms. But do you know when and how to use these different ways of bolusing your insulin?
Most people on insulin pump therapy use NovoLog (insulin aspart), manufactured by Novo Nordisk Pharmaceuticals, or Humalog (insulin lispro), manufactured by Eli Lilly and Company. Both are considered rapid-acting insulins.
NovoLog starts to work in 10 to 20 minutes. It is working at its best in one to three hours, and it is finished working in three to five hours.
Humalog starts to work within 15 minutes. It is working at its best in one to one and a half hours, and it is finished working in three to four hours.
Either insulin is well matched to the digestion of carbohydrates when given as a normal bolus immediately before you eat. With meals that contain a higher proportion of protein or fat, however, you may need to use a different bolus method in order to achieve your blood-glucose goals.
A normal bolus is the way most pump users are accustomed to giving their insulin. You calculate the amount of insulin you need (based on your carbohydrate intake or your physician’s recommendations), push a few buttons on your pump and receive the insulin over a very short period of time. For meals with carbohydrates and average amounts of protein and fat, this is the best way to take your insulin.
Extended or Square-Wave Bolus
An extended or square-wave bolus is programmed to deliver insulin evenly over a specified amount of time—anywhere from 30 minutes to four or eight hours, depending on the pump you use. You might find this useful in specific situations such as the ones described in this list.
- When you attend parties or special occasions where you are eating over a long period of time (a wedding reception, banquet, cocktail party, or holiday dinner, for instance)
- When you eat especially slowly (think of eating popcorn at the movies)
- When your rate of digestion is slow, either because you suffer from gastroparesis (delayed stomach emptying) or because you have eaten a high-fiber or low glycemic index meal (for instance, one that contains dried beans or lentils)
- When you eat a meal that is lower in carbohydrates and higher in protein or fat and thus is digested more slowly (an 8-ounce steak with nonstarchy vegetables and salad, for example)
The duration of time you program for an extended or square-wave bolus depends on the situation. When you are eating over a longer period of time, you can estimate your anticipated insulin needs and program your pump to deliver insulin for the time you’re eating.
If you experience delays in stomach emptying or if you are consuming a high-fiber meal or snack, you can calculate your insulin needs and then extend the bolus over three to four hours.
Combination or Dual-Wave Bolus
A combination or dual-wave bolus is a normal bolus plus an extended or square-wave bolus.
You can program your pump to deliver a certain amount of insulin immediately, followed by an extended or square-wave bolus. By delivering your insulin this way, you may be able to avoid the low blood glucose that some people with diabetes experience with mixed meals.
This type of bolus might be useful for the following situations:
- When you want to “cover” the first carbohydrates you eat at a meal or party, followed by continued eating at a slower pace
- When you eat a meal that contains carbohydrates and higher-fat foods (an 8-ounce steak, a baked potato with sour cream, a roll with butter and salad with dressing; or a fast-food cheeseburger and french fries)
- When you eat a meal containing certain ethnic foods that digest more slowly, including pizza and other Italian food, Chinese food, or Mexican food
In order to match your insulin needs with a meal containing carbohydrates and a high proportion of fat, you can try to divide your bolus as 50 percent normal and 50 percent extended over three to four hours.
For example, if you go to a fast-food restaurant and have a quarter-pound cheeseburger, large fries and a diet soda, you will be consuming 106 grams of carbohydrates and 56 grams of fat. If you use an insulin-to-carbohydrate ratio of 1 unit per 15 grams, you will need to bolus 7 units.
If you take all 7 units as a normal bolus, you could experience low blood glucose shortly after eating because the high fat intake can delay absorption of the carbohydrates. Instead, try to take 3.5 units immediately and then extend the other 3.5 units over the next three to four hours.
Remember that these suggestions for using the different bolus methods are only guidelines. You need to test your blood glucose frequently, keep good records and monitor the levels closely. I encourage you to experiment and use pre- and post-meal blood-glucose monitoring to find what works best for you. Working with your physician, a pump trainer or a diabetes educator experienced in pump therapy can be helpful in fine-tuning your use of these special bolus features.