Insulin is most rapidly absorbed when injected in the abdomen.

Medications & Therapies

Insulin therapy is the central and indispensable fact of medical treatment for people with type 1 diabetes. They require insulin to survive, and the only ways to administer it—for now—are via multiple daily injections or an insulin pump. The options today are multitudinous, and insulin therapy must be tailored not just to the individual but to the ever-shifting circumstances of that person’s life. So, like most of the information in this section, what follows is just a sketch of how type 1’s use insulin today.

Insulin has a fascinating history and culture, well worth reading about. Available since 1925, it was initially extracted from beef and pork pancreases. For the next 50 years, researchers worked on purifying and refining these extracts. In the early 1980s, technology became available to produce human insulin synthetically, and synthetic human insulin has entirely replaced beef and pork insulin in the U.S. More recently, insulin “analogs” that offer improved absorption are replacing “regular” human insulin.

The ultimate goal of any insulin therapy is to mimic normal insulin levels. Even with current technology and understanding, injected insulin is at best a crude approximation of the sophisticated workings of the human endocrine system in a nondiabetic, which sends just the right amount of insulin to our cells whether we’re waking, eating, or sleeping. However, a basic principle is that the more frequent the insulin injections, the better you can approximate natural or normal insulin levels.

Insulin and Metabolism in Type 1

In nondiabetics, the body releases a low, background amount of insulin to keep the blood sugar controlled overnight, fasting and between meals. Eating creates a large burst of insulin, needed to dispose of all the carbohydrate or sugar being absorbed. Even smelling or chewing food cause some insulin release, getting the body ready to receive the sugar load from the meal. As food is digested, the sugar levels rise, causing a surge of insulin. Insulin levels climb rapidly and peak in about 45 minutes to 1 hour before falling back to the background or basal levels.

In normal metabolism, insulin is continuously released from the pancreas into the blood stream. Although the insulin is quickly destroyed (in 5-6 minutes), its effect on cells may last 1 1/2 hours. When your body needs more insulin, the response is instant, and its level in the blood rises quickly. When you need less, the blood levels rapidly fall.

For people with type 1, planning and taking action must stand in for what otherwise happens automatically. You must try to mimic, with injected insulin, the natural release of insulin overnight, fasting, or between meals. At mealtimes, you have to calculate how much carbohydrate you’re about to eat and how much insulin you’ll need to compensate. Instead of an immediate response to changing events, the dose of insulin is always somewhat anticipated or delayed in reaching the blood and the cells. And once you have injected a dose of insulin, it’s going to get absorbed into your bloodstream whether you need it or not.

Types of Insulin Therapy and Insulin

There’s a tremendous amount of information available about how to design an insulin regimen to meet specific blood sugar targets, about calculating insulin doses, and the different ways of getting insulin into the body. Each person, consulting with their medical team, will make these choices in tailoring their own regimen.

Just a few basics, then. About 40-50% of the total daily insulin dose is to replace insulin overnight, when you are fasting and between meals. This is called background or basal insulin replacement. The basal or background insulin dose usually is constant from day to day. The other 50-60% of the total daily insulin dose is for carbohydrate coverage (food) and high blood sugar correction. This is called the bolus insulin replacement.

  • Background or basal insulin replacement. By providing a low, continuous level of insulin, this replacement dose aims to controls glucose overnight and between meals by keeping fat in fat tissue and curbing glucose production from the liver. The rate is not usually constant: more is needed as the body regenerates during sleep.
  • Bolus insulin replacement. Provides extra insulin either of two scenarios: mealtime bolus, to cover the carbohydrate in the meal or snack; or high-blood-sugar correction bolus, to get the blood sugar back to the target level when it is too high.

Insulins are categorized by differences in onset (how quickly they act), peak (how long it takes to achieve maximum impact), duration (how long they last before they wear off), concentration (this may vary between the U.S. and other countries), and route of delivery (whether injected under the skin or given intravenously).

Two main ways of grouping insulins are:

  • Long-acting. Typically used overnight and between meals, to mimic the body’s natural continuous release of insulin at low levels during these times.
  • Fast-acting. Typically used before meals, to provide the quick bump of insulin needed to counteract food intake; and as needed to correct high blood sugars.

Most insulin regimens combine both major types in a program known as intensive insulin therapy. Again, it’s been shown that more frequent injections of insulins matched to changing metabolic needs both improves daily life for people with type 1 and reduces the risk of complications.

Insulin Pumps

An insulin pump is a small, computerized device that is programmed to deliver insulin into the fatty tissue under the skin via a thin cannula, which is inserted into the skin. The insulin pump is durable and lasts for years, but the insulin supply and certain pump components (insulin reservoir, tubing and infusion set) are changed every few days. One pump on the market works for three days and is completely disposable.

Many of the newer pumps now incorporate a continuous glucose monitor (CGM)—this combination is the closest approximation of an artificial pancreas. However, even these pumps cannot automatically sense blood glucose levels and deliver the right amount of insulin in response because the experimental software is not safe and effective enough for use outside a hospital setting.

Another advantage of insulin pumps that that they use only fast-acting insulins. Because the pump delivers tiny amounts of insulin every few minutes, longer-acting insulins are not necessary.

Because pumps provide more precise and tailored insulin delivery, they offer greater lifestyle flexibility. Tailored insulin delivery is helpful in many situations, and pumps are now much in demand. However, not everyone with type 1 is a good candidate. You need a thorough understanding of diabetes self-management skills, and reasonably good manual dexterity and vision to operate the device safely. Psychological readiness and physiological needs vary, and starting pump therapy requires commitment. It’s not unusual to check blood sugars 8-12 times per day at first to assess basal and bolus insulin needs, though with CGM one needs to self-test less often. 

Other Medications for Type 1

Besides insulin, some people with type 1 may be treated with a class of drugs called amylin analogs. Delivered by injection, these reduce sugar production in the liver and slow the absorption of food. Amylin is a hormone that is secreted with insulin from the beta cells in the pancreas It assists insulin in controlling glucose after meals and also signals satiety, suppressing the urge to eat. In diabetes, as less insulin is secreted there is also a deficiency of amylin.

People with diabetes are at increased risk for kidney and heart disease and are often treated with preventive doses of drugs such as statins and ACE inhibitors.

The whole universe of alternative and complementary medicine contains some reasonable options for improving management of type 1. Any of these should be approached with caution and consultation with your medical team.

Takeaways

  • The goal of any insulin therapy is to mimic normal insulin levels. In general, more frequent insulin injections do this more effectively. Regimens are tailored to individuals.
  • Newer types of insulin and delivery technologies can help people meet the challenge of good control, and are often more convenient. Certain advances don’t work for everyone.
  • People with T1D may also need to take other medications, such as drugs to prevent heart or kidney disease.