Insulin Types

Insulin Delivery

Insulin Pump

Additional Elements

Insulin is a hormone (made of protein) that is produced by the beta cells in the islets of Langerhans in the pancreas. The pancreas is an organ that lies across and behind the stomach. It also secretes digestive enzymes and hormones that help with the breakdown and utilization of nutrients.

Insulin is secreted in response to an increase in blood sugar levels, usually after a meal. The insulin enables glucose to enter cells inside the body to be used as energy. The amount of insulin released is a result of the amount of glucose introduced to the system.

People with type 1 diabetes don’t produce insulin and there is a portion of people with type 2 diabetes that doesn’t produce enough insulin. These groups need insulin from external sources in order to survive.

There are more than 20 types of insulin products produced in four different categories. The categories are separated by the three characteristics of insulin:
Onset- time it takes for insulin to begin working

Peaktime- the amount of time the insulin is at full strength

Duration- the amount of time the insulin is working

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The 4 different types of insulin:

Rapid-acting insulin- begin working about 5 minutes after introduction, peak at around 1 hour, and work for 2 to 5 hours

Examples:
— Humalog (lispro) by Eli Lilly: onset- 15 minutes, peak- 30-90 minutes, duration- 3-5 hours
— NovoLog (aspart) by Novo Nordisk: onset- 15 minutes, peak- 40-50 minutes, duration- 3-5 hours
Short-acting (regular) insulin- begin working about 30 minutes after introduction, peak at 2 to 3 hours, and typically work for 3 to 8 hours

Examples:
— Humulin R by Eli Lilly: onset- 30-50 minutes, peak 50-120 minutes, duration- 5-8 hours
— Novolin R by Novo Nordisk: onset- 30-50 minutes, peak 50-120 minutes, duration- 5-8 hours
Intermediate-acting (NPH) insulin- begin working about 2-4 hours after introduction, peak at 4-12 hours, duration 12-18 hours

Examples:
— Humulin N by Eli Lilly, Novolin N by Novo Nordisk: onset 1-3 hours, peak at 8 hours, duration 20 hours
— Humulin L by Eli Lilly, Novolin L by Novo Nordisk: onset 1-2.5 hours, peak at 7-15 hours, duration 18-24 hours

Intermediate and short-acting mixtures- the onset, peak, and duration are composites of the combinations

Examples:
— Humulin 50/50, Humulin 70/30, Humalog 75/25, Humalog 50/50 by Eli Lilly; Novolin 70/30, Novolog Mix 70/30 by Novo Nordisk
Long-acting insulin- begin working about 6-10 hours after introduction, peaks at 8-12 hours, duration 24-36 hours

Examples:
— Ultralente by Eli Lilly: onset 4-8 hours after introduction, peak at 8-12 hours, duration 36 hours
— Lantus (glargine) by Aventis: onset 1 hour after introduction, works evenly over a 24 hour period

Insulin strength:

In the United States it is most common to use insulin that is U-100 strength but in Europe it is more common to see the U-40 strength used. All insulin is dissolved or suspended in liquid and these names illustrate the number of units of insulin per milliliter of fluid. Therefore, U-100 has 100 units of insulin per milliliter of fluid and U-40 has 40 units of insulin per milliliter of fluid.

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Insulin delivery:

There are numerous ways to inject insulin into the body. When injected the mechanism must penetrate the skin and enter the adipose (fat) tissue beneath the skin. The syringe is the most common form of injection but other methods include pens, jet injectors, and insulin pumps.

Syringe- a hypodermic needle connected to a hollow cylinder
The size of the syringe is directly related to the dose and strength of insulin used. Some syringes are also coated to aid in injection.

Insulin pen- a pen with an insulin cartridge
The needle on a pen is similar to that on a syringe but it is retracted. When used the person adjusts the dose accordingly and then the plunger is pressed to release the needle into the skin. Some of the pens are replaceable and some are disposable. Pens do not hold multiple types of insulin, so if a person uses 2 types of insulin then 2 shots are necessary.

Jet injector- uses no needles, squirts a fine spray of insulin into the skin
These have been available for over 20 years but have not picked up steam. Their share of the market is small but there is a small portion of the population that still uses them.

Insulin pump- a reservoir of insulin, a mechanism about the size of a beeper, a plastic tube, and a soft plastic needle called a cannula
The cannula is inserted into the skin in the abdomen and is changed every 2 days. It can be disconnected for swimming and showering. The mechanism is worn outside the body and it provides constant 24 hours insulin doses. The dose is predetermined by the user and their health care professional. To date this is the closest thing to a new pancreas.

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Use of an insulin pump:

Insulin pumps were introduced to the market in 1979 and are currently used by over 50,000 people worldwide. They are commonly used by type 1 diabetics but are becoming more popular with some type 2 insulin dependent diabetics. They cost on average, $5,000-$6,000 for the pump and around $450-$500 to maintain every month.

Insulin pumps are similar to the pancreas in that they release a steady, basal, rate of insulin into the blood. Before meals they release a burst of insulin, bolus, to accommodate for the carbohydrates in the meal. They can also release a corrective dose if blood sugar levels are high before eating. This is done by pressing a button on the pump in accordance to what is needed.

People who choose to use insulin pumps must be able to check blood sugar levels at least 4 times per day, before each meal, and before bed. They must also remember to bolus before meals. Counting carbs is also important because it directly relates to the dose of insulin necessary to compensate for them.

According to the ADA it is important to remember a few tips when removing the pump:
Don’t remove the pump while it is releasing a bolus as it will NOT resume delivery when reattached.
You must bolus to cover the insulin you will miss while the pump is removed unless your blood glucose level is under 150, in which case you can wait an hour.
— DO NOT go more than 2 hours without insulin
— Make sure to check blood glucose

There are advantages and disadvantages to using a pump including:

Advantages:
— Don’t need individual injections
— More flexibility in what you eat
— Helps level A1C levels
— Precise, predictable insulin delivery
— Reduces chances of severe episodes of hypoglycemia
— Helps manage the dawn phenomenon

Disadvantages:
— Mechanical advice that requires maintenance
— Battery runs out
— Delivery system gets clogged
— Injection site gets inflamed or infected (must change site regularly)
— Forget to bolus
— Can cause weight gain
— Can cause ketoacidosis

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Insulin additives:

There are additives in all insulin to enhance them in one form or another. Some kill bacteria or maintain a constant pH and some enhance the action of the insulin. In rare cases there can be an allergic reaction to the additives.

Insulin storage:

Insulin should be stored in a refrigerator to maintain freshness. This can potentially make the injection more painful so the insulin bottle being used can be stored at room temperature. When stored at room temperature the life of a bottle of insulin is approximately 1 month. Extreme temperatures can spoil the insulin so it is not recommended to freeze or heat insulin. Never use insulin that is past expiration or shows signs of spoil.

Injection:

When injecting insulin it is necessary to rotate sights from one body part to another, at least 1 inch from the last injection site and preferably in another body part. Continuous use of the same site can lead to scarring and decreased absorption. Different body parts also affect insulin absorption due to the amount of tissue at the injection site.

Reusing the same syringe is not recommended but can be done if proper precautions are taken. The syringe must be resterilized but manufacturers won’t guarantee the sterility of reused syringes. This is not recommended if the user is ill or if they are easily susceptible to disease. The sharing of needles is dangerous and is strongly recommended against.

Disposal:

Take precaution when disposing of used syringes. If possible, clip the needle off of the syringe to prevent it from sticking anyone. Recap the syringe and/or place it in a heavy duty container or box and dispose of it in proper disposal sites.

Schedule:

The schedule of insulin injections is different for everyone, depending on a number of factors.

People who suffer from type 1 diabetes typically start with 2 shots per day with a combination of insulin types. This progressively grows to 3-4 injections per day with combinations of insulin. According to the ADA this is done to delay the onset of complications including nerve, eye, and kidney damage.

People with type 2 diabetes vary in their schedule because of the difference in severity of their condition. Some of the type 2 diabetic population can be successful without using insulin. Oral medications are sufficient because they still maintain enough insulin production and sensitivity to maintain relative homeostasis. They typically begin with one injection per day, typically at night, and move up to 3-4 injections per day depending on the case.

The time and dose of insulin is also specific to each person. Insulin is most effective when the proper dose is taken at the proper time. Some insulins are designed to be taken before meals or before bed. The timing of these doses is designed to make them optimally effective.

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