Fact sheet: Insulin therapy

What is insulin therapy?

Everyone who has type 1 diabetes, and some people who have type 2 diabetes, need insulin therapy. There are different types of insulin available for treating diabetes. They differ in terms of how long it takes for them to start working and how long their effect lasts, as well as in their chemical structure. Some types of insulin work quickly (rapid-acting or short-acting insulin), while others only start to work after a certain amount of time, or work over a longer time period (intermediate-acting or long-acting insulin).

It is important for people with diabetes to understand the goals of their insulin therapy and know how to reach them: Insulin is injected to make up for the lack of insulin in the body and lower the blood sugar levels. Blood sugar levels should be prevented from getting too high or too low. Insulin therapy also aims to prevent long-term complications associated with diabetes.

Blood sugar levels are not only affected by the amount of insulin you inject but also by what you eat and drink, as well as how much energy you use during physical activity. The time of day, inflammatory diseases or hormonal changes can influence your blood sugar levels too. This means that people with diabetes have to be familiar with their own body and know how it reacts to everyday activities so that they can adjust the amount of insulin they take accordingly.

Why do so many people with diabetes have to inject insulin?

Our bodies need insulin to convert food into energy. Insulin is a hormone that is produced in the pancreas and released into the blood. The pancreas is an organ found behind the peritoneum (the membrane lining the abdomen) and below the stomach.

 

Insulin and glucose (sugar) are transported in the blood to the cells of the body. There the glucose enters the cells with the help of insulin. Insulin fits into parts of the cells, called receptors, like a key. It “opens the door” to the cells, allowing glucose to enter. Then the cells can use the glucose as fuel for the body. Without insulin, many organs cannot take in sugar from the blood to make use of it in the cells. This means that there are high levels of sugar in the blood and the organs cannot work properly.

In people with type 1 diabetes, the insulin-secreting cells of the pancreas are destroyed. Insulin, which we need to live, can no longer be produced. People with type 1 diabetes have to inject insulin every day in order to give their body a constant supply of the hormone.

People with type 2 diabetes also have high blood sugar levels. Although the pancreas still produces insulin, it either does not produce enough or the cells cannot use the insulin effectively. The result is the same as in people with type 1 diabetes: higher blood sugar levels. In people who have type 2 diabetes and are overweight, the reason why insulin produced in the body does not work properly anymore is often because the cells are no longer sensitive enough to it. So, at first, the aim of treatment is to make the cells more sensitive to insulin again. Losing some weight and doing more exercise often already makes a difference. In many people with type 2 diabetes, this can make their cells respond better to insulin again. If it is necessary to lower blood sugar levels, but losing weight and doing more exercise are not enough, drugs that help to reduce blood sugar levels (oral antidiabetics, for example) can be used. You can read more about these drugs here.

If these do not help anymore either, or if they do not agree with the person, insulin therapy is needed.

What types of insulin are there?

There are different types of insulin. Insulin is not available as a tablet or capsule because the stomach acid would damage the hormone if swallowed, so it would not work. All types of insulin lower blood sugar – some do so faster, others slower. How much the sugar is lowered depends on the dose. Some types of insulin cover the basic needs of your body: they work slowly and constantly over half a day or a day. This is called “basal rate” of insulin. Other types, known as “mealtime” or “bolus” insulin, are used in addition to the basal rate at mealtimes.

Insulin can be extracted from the pancreas cells of pigs (porcine insulin) or cattle (bovine insulin) and prepared for use in humans. Nowadays, however, the insulin used for treating diabetes is usually produced artificially. One type, known as “human insulin”, is chemically identical to the insulin produced naturally in the human pancreas. There are also other artificially produced types of insulin called “insulin analogues”. They have a slightly different chemical structure from other kinds of insulin. So far there has been no research on the possible long-term effects of insulin analogues.

Recent research has given rise to the suspicion that one of these artificial kinds of insulin (insulin glargine) might speed up the development of cancer. Further data needs to be analyzed to be sure about this safety issue though. People who have diabetes and use glargine have many other options, including human insulin. You can read more about the different insulin therapy options here.

Researchers have developed various insulin products over the last few decades. They differ in how fast they start to lower blood sugar levels, as well as how long their effects last, and are classified as follows:

• Short-acting and rapid-acting insulin:
  
  Insulin analogues:
  Start working about 5 to 10 minutes after injection
  Peak activity about 1 to 1.5 hours after injection
  Work for about 2 to 3 hours
  
  Regular (unmodified) insulins (human insulin, porcine insulin, bovine insulin):
  Start working about 15 to 30 minutes after injection
  Peak activity about 1.5 to 3 hours after injection
  Work for about 4 to 8 hours after injection
   
• Intermediate-acting insulins (insulin analogues, human insulin, porcine insulin):
  Action delayed or prolonged with NPH (neutral protamine Hagedorn) or zinc:
  Start working about 2 hours after injection
  Peak activity about 4 to 6 hours after injection
  Work for about 12 to 14 hours
   
• Long-acting insulins (insulin analogues, human insulin, porcine insulin):
  Slower to start working
  Peak activity and how long they work for depend on the way in which they are delayed or prolonged
  Usually work for up to 24 hours

 

• Premixed insulin (insulin analogues, human insulin, porcine insulin):
  Short-acting insulin and intermediate-acting or long-acting insulin that have already been mixed

Short and rapid-acting forms of insulin, including regular insulin, insulin analogues or premixed insulin, are normally injected before meals. Some people wait a certain amount of time following the injection before they eat. Others vary the time interval between injecting and eating depending on their blood sugar levels.

Many people find that fixed injection-meal intervals are bothersome and difficult to stick to in everyday life. So far there is no evidence to show that blood sugar levels can be controlled better by following fixed injection-meal intervals.

A new insulin product entered the market at the beginning of 2006: inhaled human insulin (brand name: “Exubera”). On October 18, 2007 the manufacturer of this product announced that it would be taken off the market. Exubera is no longer available. It is not clear whether other manufacturers might produce inhaled insulin in the future.

Inhaled insulin is dispersed using an inhaler. The insulin is breathed deeply into the lungs where it reaches the alveoli (air sacs) and enters the blood. Inhaled insulin is a short-acting insulin. If long-acting insulin is also needed, it has to be injected in addition to using the inhaler. Inhaled insulin is not suitable for people who smoke or have a severe chronic lung disease such as asthma or COPD (chronic obstructive pulmonary disease – chronic bronchitis or emphysema). So far, the possibility that long-term use of inhaled insulin could be associated with risks has not been ruled out. A lung function test should be carried out before starting treatment with inhaled insulin, and then every six months after that.

What is conventional insulin therapy?

Most people with type 2 diabetes who use insulin inject it twice a day. This is called conventional insulin therapy. People who prefer a certain routine in everyday life, with fixed injection times, choose this option.

This treatment can either be carried out using long-acting insulin alone or together with normal insulin. In most cases a standard mixture of normal and long-acting insulin is used and injected before breakfast and evening meals. It is important to eat regularly throughout the day in order to balance the effect of the insulin in the blood. People who do a lot of physical exercise can make up for it by eating additional snacks. In conventional insulin therapy, meals and physical exercise are adjusted to the effect of insulin.

This kind of therapy can sometimes mean leading a rather regimented lifestyle. However, it does suit the insulin needs and usual habits of some people with type 2 diabetes.

What is intensive insulin therapy?

In intensive insulin therapy the amount of insulin is adjusted according to blood sugar levels, physical activity, and the amount of food a person eats. Regular blood sugar monitoring is essential here. You can either inject yourself several times a day or use a pump to supply the hormone. In order to accommodate the body’s basal insulin needs, long-acting insulin can be injected once or twice a day. Short-acting insulin is injected before each meal to handle the carbohydrates that are eaten. If people use a pump, only normal insulins or short-acting insulin analogues are used. The pump regularly injects small amounts of this type of insulin to continuously cover the basic needs of the body.

Intensive insulin therapy should make it possible to have near-normal blood sugar levels. It allows you to be flexible because you do not have to eat at certain times of the day or be careful to always eat the same amount of carbohydrates. Research suggests that intensive insulin therapy can reduce the risk of complications caused by type 1 diabetes.

How is insulin taken?

The oldest method is using a normal syringe to draw up the insulin. Later on, researchers developed insulin pens insulin pumps and jet injectors. Many people prefer to use insulin pens. Insulin pens look a bit like fountain pens. Different types of systems are available that use insulin-filled cartridges to be put in. Insulin-pens are generally user-friendly and make it easy to dose your insulin. Different types of systems are available. There are also disposable pens, which are pre-filled, and the whole pen is thrown away when empty.

Modern insulin pumps are roughly the size of a mobile phone. They have a cartridge filled with short-acting insulin. The hormone enters the body through a tube attached to a fine cannula which is inserted into the skin of the abdomen. The pump is programmed to regularly release a small amount of insulin, the basal rate, into the body. At mealtimes a bolus  dose of insulin is additionally injected by the user at the touch of a button. The amount of insulin injected depends on the blood sugar reading taken shortly before. Similar to when using syringes, the person with diabetes has to regularly measure the blood sugar levels, estimate the amount of carbohydrates in the meal, and then adjust the insulin dose accordingly.

When using a jet injector, the user presses insulin underneath the skin without using a needle. Jet injectors are bigger and somewhat less user-friendly than insulin pens. Not many people use them.

Whether you use a syringe, an insulin pen or a pump, everyone with diabetes who needs insulin has to have training in order to treat themselves in an independent and safe way.

Why can insulin therapy lead to low blood sugar?

Whenever insulin is artificially supplied to the body, there is always a risk of low blood sugar (hypoglycemia). Even if you take your blood sugar and physical activity levels into account, estimate the amount of carbohydrates in your food and precisely calculate the insulin dose required, you can still inject too much insulin. If this happens, your blood sugar levels drop below the normal range of 60 milligrams per deciliter (3.3 mmol/L).

Signs of hypoglycemia often include paleness, sweating, shaky hands and food cravings. People find it hard to concentrate and are sometimes confused. If you experience these symptoms it means that your blood sugar levels are too low and you should eat glucose or drink sugary drinks. This helps to rapidly restore your blood sugar levels, almost immediately making you feel better. That is why everyone who takes insulin should always carry glucose with them just in case.

No matter what kind of insulin therapy you choose, effectively managing your diabetes requires a lot of effort and energy. It is not always easy, but it is worth it: if treated properly, your chances of developing complications associated with diabetes are much lower. It is important that you know your body well and choose the insulin therapy approach that suits you best.

Author: Institute for Quality and Efficiency in Health Care (IQWiG)

© IQWiG (Institute for Quality and Efficiency in Health Care)