By: Barry Ginsberg
This is the second part of a three-part series called “Intensive Insulin Therapy,” written by Dr. Ginsberg in response to the DCCT results. Part one defined intensive therapy and gave an overview of the theories and techniques involved. The second part explains how to start an intensive therapy regimen and calculate your daily insulin doses. The third will deal with adjusting insulin doses when using intensive therapy. The goal of this series is to educate people with diabetes about intensive therapy and enable them to choose the therapy that is right for them.
Dr. Barry H. Ginsberg, MD, PhD, and Endocrinologist, is currently the Medical Director for Becton-Dickinson, the largest manufacturer of syringes in the United States. The opinions in this article are those of Dr. Ginsberg and do not necessarily represent those of Becton-Dickinson and Company.
Starting Intensive Insulin Therapy
Intensive insulin therapy is a part of an entire intensive therapy program, including diabetes education, a well-planned nutrition and exercise program, and accessibility to an effective diabetes treatment team. It includes intensive insulin therapy, intensive blood glucose monitoring, intensive nutrition, intensive education, and intensive interaction with the health care team. Currently, this is generally available only at a diabetes center, but soon a new program called Staged Diabetes Management will make this widely available. Patients should not attempt to start intensive insulin therapy by themselves, but rather should seek the aid of a knowledgeable physician to help them. In this section I present the methods that I use to start intensive therapy. You can use this as a basis for deciding if intensive insulin therapy is for you and to use the general themes involved to understand why your diabetes treatment team is using certain methods.
In starting intensive insulin therapy, you first need to determine the total insulin dose. There are three general methods for doing this. The most elegant, but most difficult and expensive, is to admit you to the hospital and place you onto an artificial pancreas (called a Biostator) for a day. Although this is done at a few diabetes centers, it is too inconvenient and expensive for general use. A second method is to assume that you have a sensitivity to insulin that is about average and therefore that you need about 0.275 Units of insulin per pound of your ideal body weight. A third method is to assume that your current insulin dose is approximately correct, and so if you add up all of your insulin components of all of your injections, that sum will be about the right starting dose. None of these methods has been proven clinically superior. I generally use the last method.
Basal and Bolus Doses
The insulin will be used for two separate purposes by your body: to provide a baseline amount of insulin to allow utilization of the sugar made by your liver, called a basal dose, and insulin for each meal, called bolus doses. In figure 3 we show the insulin profile broken into these two components. The basal component is generally flat, or nearly flat, whereas the bolus component has a peak for each meal.
In all forms of intensive insulin therapy, the bolus doses are designed to match the food that you eat. These doses are always given as regular insulin. Because the insulin needs to be absorbed rapidly, it is usually injected in the abdomen. Injections in the abdomen are generally absorbed about 15 minutes earlier than those into the arm and about 30 minutes earlier than those given into the thigh. Even injections into the abdomen take about 90 minutes to get into the blood stream and since an average carbohydrate is absorbed in sixty minutes, the injections should be given 30 minutes before a meal. Thus, in intensive therapy, about 30 minutes before you eat you should check your blood sugar, determine your dose of regular insulin, and take an injection into the abdomen. You do this whether you eat lunch at 11 AM, Noon, or 3 PM. This gives you greater flexibility in your lifestyle, since you are not tied down to highly specific mealtimes.
Basal doses are more complicated. In the simplest regimen, in which the basal dose is given as the very long lasting insulin UltraLente, you simply take 1-2 doses of the insulin each day. In some patients, the basal dose is more complicated. In these patients, the basal is provided by NPH insulin at bedtime plus regular insulin during the day. The NPH provides the basal insulin during overnight and a few extra units of regular insulin, given with each bolus dose, provide the “basal” during the day. With this type of regimen, you must eat at least every six hours during the day or you will run out of the regular insulin that provides the basal. With the UltraLente regimen it is possible (but difficult) to skip meals.
Determining Starting Doses
In determining a starting dose for intensive insulin therapy, I use the rules in Table 1. The total dose is determined as described above. The basal dose of UltraLente is up to 0.1 units per pound of ideal body weight (IBW) or of NPH up to 0.05 units per pound of IBW per day. The total bolus dose (all regular) is determined by subtracting the total basal dose from the total dose and then 40% is given at breakfast, 25% at lunch and 35% at supper.
For example, if a 140 pound teenager were on a regimen of NPH 15, Regular 8 in the morning and NPH 10, Regular 7 in the evening, his total dose would be 40 units. With a weight of 140 pounds, his basal dose might be 7 units of human UltraLente in the morning and 7 units in the evening, for a total of 14 units of basal dose (using table 1). His bolus dose would be the total dose less the basal dose, or 40-14 = 26 units, and therefore the individual doses would be 10 units at breakfast (40% of 26), 7 units at lunch (25% of 26 units) and 9 units at supper (35% of 26 units).
The starting dose needs to be adjusted frequently as described in the next section.
DIABETES HEALTH Disclaimer: You should consult your diabetes professional before changing insulin doses.
“Intensive Insulin Therapy” concludes next month, when Dr. Ginsberg tells you how to adjust your insulin doses. If you can’t wait for the rest of this article, send a self-addressed, stamped envelope and $1 to: Dr. Ginsberg c/o DIABETES HEALTH, 3715 Balboa Street, San Francisco, CA 94121.