by Ann S. Williams, MSN RN CDE
This column focuses on providing information to help people make their diabetes care fit their needs and their lives.
One of many technical advances in diabetes care over the last several years has been the release of several new types of insulin. This has opened many possibilities for new insulin regimens that match people's needs more closely than the old ones did. Now, people often find they can have both better diabetes control and greater lifestyle freedom. In other words, many people are finding that they can literally "have their cake and eat it too."
Normal Insulin Secretion
To understand ideas about the newer insulin delivery patterns, let's look first at normal insulin secretion in someone who does not have diabetes. The main purpose of insulin is to stimulate the body's cells to take in glucose (the form of sugar that is dissolved in the blood, the major source of fuel for the body's cells). A second purpose is to signal the parts of the body that store glucose, like the muscles and the liver, to keep it stored -- in other words, not to release it into the bloodstream.
In someone who does not have diabetes, the pancreas normally secretes a small amount of insulin 24 hours a day, seven days a week, even when the person does not eat. This background insulin is known as "basal" insulin. It is necessary because the body's cells need to take in glucose all the time, even when the person is totally relaxed or even asleep.
After all, the cells need to burn glucose for the energy they need just to
stay alive. Furthermore, the insulin signal that tells the muscles and liver
to keep the stored glucose in storage is also important. If that signal was
not there, the stored sugar would be released when it's not needed, and the
blood sugar would rise too high.
For most people, the basal insulin need is relatively steady throughout the day, at somewhere between 0.5 - 2.0 units. But some variation throughout the day is also normal. For example, many people need a little extra basal insulin during the early morning hours, and a little less basal insulin during exercise. When the pancreas is working properly, it adjusts for these variations and produces the exact amount of insulin the body needs, just when the body needs it.
When a person eats something that contains carbohydrates (starch or sugar), digestion begins immediately. The first carbohydrates to enter the stomach are broken down into glucose, which makes the blood sugar begin to rise in just about 10-20 minutes. In a person who does not have diabetes, the pancreas works a little like a thermostat. A thermostat senses cold and responds by turning on the heat. The pancreas senses a rise in blood sugar and responds by secreting insulin. When insulin made by the pancreas enters the body, it acts very quickly to lower blood sugar. If the person eats only a little carbohydrate, the pancreas puts out only a little insulin; if the person eats a lot of carbohydrate, the pancreas puts out a lot of insulin. And, just as a thermostat turns off the heat when the temperature returns to normal, the pancreas stops secreting insulin when the blood sugar returns to normal.
Insulin Types and Action
Now let's look at the action times of insulin most commonly used in the United
States. The following list gives basic information about each major type of
insulin, from the fastest and shortest acting to the longest acting. (It does
not include animal-source insulin or Ultralente, which are seldom used in the
Insulin: Humalog (Lispro)
Begins working: 15-20 minutes
Peaks at: 1-2 hours
Ends working: 3-4 hours
Insulin: Novolog (Aspart)
Begins working: 15-20 minutes
Peaks at: 1-2 hours
Ends working: 3-4 hours
Begins working: 30-60 minutes
Peaks at: 2-3 hours
Ends working: 6-7 hours
Begins working: 2-4 hours
Peaks at: 6-10 hours
Ends working: 14-16 hours
Begins working: 3-4 hours
Peaks at: 6-12 hours
Ends working: 16-18 hours
Begins working: 4-6 hours
Peaks at: 10-16 hours
Ends working: 18-20 hours
Insulin: Lantus (Glargine)
Begins working: 2-3 hours
Peaks at: Almost no peak
Ends working: 18-24 hours
All these different types of insulin have been used in multiple combinations, and every combination seems to work well for someone. In general, when designing an insulin regimen for an individual, you're trying to get the blood sugar as close to normal as possible without too much hypoglycemia (low blood sugar), without too much inconvenience, and at a cost the person can afford.
Making Insulin Work For You
Now let's think again about normal insulin secretion. Natural human insulin
secreted by a pancreas is very rapid-acting insulin. If we think about the insulin
described above, the closest we could get to the way the body actually produces
insulin would be to deliver tiny amounts of rapid insulin (Humalog or Novolog)
throughout the day, and then to give larger amounts with meals, to match the
carbohydrate in the meal. Following are three commonly-used insulin regimens,
and some discussion about how well they match the body's needs.
All-rapid insulin in an insulin pump: An insulin pump is designed to work very closely to natural insulin secretion. It is programmed to give tiny amounts of rapid insulin throughout the day, and the pump user then triggers larger amounts (bolus) at mealtimes. Unfortunately, unlike a pancreas, the insulin pumps currently available do not automatically sense the blood sugar and give the right amount of insulin. Instead, people who use insulin pumps learn to adjust the amount of insulin the pump delivers throughout the day (the basal insulin), and to give themselves the right amount of insulin with food (the bolus insulin), and to adjust for unexpected high blood sugar. If the basal insulin need varies throughout the day, they can set the insulin pump to give different amounts at different times. In other words, they learn to "think like a pancreas." This allows them to eat what they want when they want, to not eat if they don't want to, and to adjust the insulin to exactly what they need in any situation. Properly taught and adjusted, an insulin pump can come very close to normal insulin secretion, and give excellent blood sugar control with little or no hypoglycemia. Using an insulin pump does require extra work, and some inconvenience: frequent blood sugar checking, calculation of insulin for each meal, the constant presence of the pump itself, and the need to fill the pump with insulin and change the tubing at least every three days. People who like using insulin pumps generally say that the inconveniences of pump use are small compared to the increased freedom in eating times, and the feeling of well-being they have with better blood sugar control. However, not everyone feels those inconveniences are small, and using an insulin pump can be very expensive for people who don't have insurance coverage. (Editor's Note: For years, many blind diabetics have successfully used insulin pumps.)
Long-acting (basal) and rapid (bolus) insulin: The next closest to normal insulin secretion involves using two kinds of injected insulin: Lantus for the basal insulin, with a rapid insulin (Humalog or Novolog) with meals. Lantus insulin lasts in the body for about 24 hours, and has no peak, so it can make a very good basal insulin. And since the rapid insulins go into the body very quickly, they can be given right before a meal, and adjusted to cover the exact amount needed for that meal. This insulin regimen is so close to the way insulin is given with a pump that it is sometimes called "the poor man's pump." It involves the work of learning to adjust the insulin for meals and for high blood sugar, and in turn allows the freedom of eating as much or as little as the person wants, or even skipping meals. Many people are able to get excellent control with this pattern, without the expense of a pump and the inconvenience of wearing a pump all the time. This combination of types of insulin does have a few disadvantages, though. With Lantus insulin, it is impossible to vary the basal insulin throughout the day, so people who need that variation would not get quite as good control as with an insulin pump. The person must inject insulin, on average, four or more times a day: rapid insulin whenever eating a meal or a carbohydrate-containing snack, and a separate Lantus injection, because Lantus cannot be mixed with any other insulin. (Lantus is usually given at bed time.) Also, since both the rapid types of insulin and Lantus are still relatively new, they are more expensive than the older types of insulin.
Intermediate and short-acting mixture: Before Lantus and Humalog became available,
the choices in injected insulin were less like normal insulin secretion. Generally,
most people in the U.S. used some combination of a short-acting insulin (Regular)
and an intermediate-acting (Lente or NPH) insulin. A typical regimen would be
to take a mixture of these two insulins about 1/2 hour before breakfast, counting
on the short-acting insulin to cover the blood sugar rise from breakfast. The
intermediate-acting insulin would provide for both the basal insulin need through
the day, and also its peak mid-day would cover the insulin need for lunch. A
second injection of a mixture about 1/2 hour before suppertime would provide
rapid insulin to cover the supper need, and the intermediate-acting insulin
to cover the overnight basal need. (More recently, people often use a combination
of intermediate and rapid insulin in the same way; but rapid insulin can be
given right before a meal, making the timing of the injection a little easier.)
This insulin regimen has the advantage of being simple, not requiring the mental
arithmetic of figuring out doses, only requiring a minimum number of injections,
and not being very expensive. But, it has the disadvantages of not being very
precisely adjusted to a person's need, and not allowing much flexibility in
eating. For example, once the intermediate insulin is injected in the morning,
it will peak a few hours later whether lunch is ready or not. If the person
does not eat enough food at the right time, a dangerously low blood sugar can
be the result. This is usually not a problem for people who keep regular schedules
and do not mind having to eat about the same amount every day. But for people
who want flexibility it can feel too rigid.
What is right for you? These are only a few of the possible insulin regimens. How can you decide what is right for you? The following questions can help point you in the right direction:
1. Is excellent control of your diabetes important to you?
2. Do you want to have flexibility in when you eat and how much you eat?
3. Have you had a lot of problems with frequent episodes of low blood sugar?
4. Are you willing and able to pay attention to your diabetes (checking your blood sugar and giving yourself insulin) before eating every meal?
5. Are you willing and able to learn carbohydrate counting and the simple mental arithmetic to adjust your own insulin doses to your need?
6. Do you have good insurance coverage or adequate financial resources for insulin, diabetes equipment, and diabetes supplies?
7. Is a simple diabetes regimen important to you?
8. Are the timing and amounts of your meals regular, with little change from day to day?
9. Have you been able to get easy control of your blood sugar with relatively little effort?
10. Would paying attention to your diabetes at every meal be difficult for you?
11. Do you have little or no insurance coverage, and not much financial resources for insulin, diabetes equipment, and diabetes supplies?
If you answered "Yes" to Questions #1-#6, you should probably consider using an insulin pump, or a Lantus and rapid insulin regimen. If you answered "Yes" to Questions #7-#11, you should probably consider using a combination of intermediate and regular or rapid insulin. If your answers didn't divide up so evenly, then you'll need to consider closely what is most important to you.
No matter what you answered to these questions, it is important for you to be aware that you have many possible choices. It is best if you can discuss these choices, and other choices too, with a diabetes educator or physician who knows about the full range of possibilities. That will give you the best chance of figuring out an insulin regimen that will fit your individual needs, and allow you to live your life to the fullest.
Readers: Do you have questions about how to make your diabetes care fit your life? If so, please send them to the Voice editor, and I'll answer in a future column.