The most common way to take insulin is as a subcutaneous (under the skin) injection at a site where there is fat tissue. The most common injection sites are the abdomen (except for a 2-inch area around the navel), the front and outer side of the thigh, the upper part of the buttocks, and the outer side of the upper arm. Many people find that insulin is absorbed fastest from the stomach area.
When you first begin insulin treatment, you'll probably use a needle and syringe for your injections. Your doctor or nurse educator will show you how to load the syringes, how to inject yourself, and how to rotate injection sites to prevent damage to any one area and to provide the absorption speed that meets your needs. When you become more experienced at the injections, you may explore other options, such as insulin pens, jet injectors, or an external insulin pump.
For years, injection of insulin with a needle and syringe was the only option. Syringes are still the best choice for most people who mix different types of insulin for a single injection. Fortunately, the syringes currently available—disposable, lightweight syringes with shorter, ultrafine needles—make daily injections more convenient and less painful. They come in a wide variety of sizes and styles, so you’ll want to experiment to find the size that works best for you. For example, individuals who are overweight may not be able to use very short needles.
Insulin pens combine an insulin container and syringe in one compact device. Two types are available: reusable and prefilled. With reusable pens, you load a cartridge of insulin into the pen, attach a needle, dial in your insulin dose, and press the plunger to administer the injection. Prefilled pens contain a built-in insulin cartridge and are even easier to use, although they can be expensive. After the insulin is used up, you throw the prefilled pen away.
Jet injectors use a high-pressure jet of air to send a fine stream of insulin through the skin. Although jet injectors eliminate the need for needle sticks, they cause as much pain as insulin injections and often result in bruises. In addition, jet injectors are bulky and expensive, adding to the reasons they are not widely used.
External insulin pumps
Some people who require frequent insulin injections do better with an external insulin pump, which more closely mimics the work of the pancreas. The pump is a small, portable device (usually worn at the waist) that delivers insulin through a tube (a catheter) attached to a small needle inserted just below the skin of the abdomen or thigh.
The pump is easy to use. It is programmed to automatically deliver a continuous amount of insulin throughout the day. Before meals, the user presses a button to deliver the extra insulin needed.
Insulin pumps are primarily used by people with type 1 diabetes, but more type 2 patients are starting to use the pump. The biggest advantage of the pump is improved blood glucose control. For example, in a four-month study of 79 people, pump users had an average HbA1c level that was 0.8 percentage points lower than that of people on injected insulin therapy.
There are drawbacks to insulin pumps, including the need for frequent blood glucose monitoring. However, some newer pumps are equipped with glucose meters; one, the Medtronic Minimed Paradigm, recommends bolus dosages based on current blood glucose levels, how much insulin remains in your body, and how many carbohydrates you expect to eat in your next meal. Users must also be vigilant for skin infections, pump malfunctions, leaks in the catheter, and inadvertent removal of the needle from its site beneath the skin. Any of these interruptions in the insulin infusion can cause a rapid fall in blood insulin levels that could result in ketoacidosis in people with type 1 diabetes.
Now that long-acting insulins like Lantus and Levemir are available, they may be a more practical choice than the pump for some people. Studies have shown that once-a-day injections of Lantus plus Humalog or Novolog injections prior to meals is a close second to the efficacy of pump treatment.
In 2006, the FDA approved Exubera, the first inhaled insulin. Exubera was a dry powder administered with a device similar to an asthma inhaler. It could take the place of premeal insulin injections but could not be used as a substitute for longer-acting insulin needed in the morning or before bed. Exubera was pulled from the market in late 2007 due to low sales, partly because of concerns from doctors whether it was safe for the lungs.
Other inhaled insulins are under consideration.
Techniques under development
Researchers are working on several new approaches to insulin delivery, including nasal sprays, pills, and skin patches.
Also in the works is an implantable insulin pump, which is placed under the skin on the left side of the abdomen. The pump delivers insulin in small, intermittent pulses at a constant rate via a catheter. The insulin pulses are supplemented by mealtime doses of insulin that are controlled with an external device that transmits commands to the pump. Needle injections are required only every few months to refill the pump.