How is insulin used to treat type 2 diabetes?
In type 2 diabetes, the body loses the ability to use the insulin it produces effectively (this is called “insulin resistance”). In addition to insulin resistance, loss of the ability to produce insulin also plays a role in elevated blood glucose in type 2 diabetes. In fact, by the time that most people are diagnosed with type 2 diabetes, they have already lost over 50% of their ability to make the insulin they need.1-2
Physicians and diabetes experts have varying viewpoints on when insulin should be started in the treatment regimen. Some believe that initial treatment should be oral diabetes medication then adding insulin if there is insufficient glycemic control. Others believe that starting insulin therapy earlier may preserve the ability of the pancreas to continue to produce insulin. The American Diabetes Association (ADA) recommends using metformin as initial medical treatment for blood glucose in type 2 diabetes. However, in certain situations (people who have high blood glucose levels (over 300 mg/dL and/or A1C greater than 10%) the ADA guidelines recommend that insulin should be considered as initial therapy, with or without other treatments. Determining the optimal treatment for the individual person involves many considerations, including the effectiveness of the treatments, the risk of hypoglycemia (low blood sugar), impact on weight, potential side effects, cost, and the patient’s preferences.3,4
What are the types of insulin?
There are two main types of insulin preparations: insulin preparations that are identical to human insulin (these are often called “human insulin preparations”) and insulin analogs.5
Human insulin preparations are synthesized (they are made in a production facility) based on the molecular structure of human insulin produced by the body. These insulin preparations are identical to naturally produced insulin.
Human insulin analogs (the word “analog” literally means “similar” or “comparable”) are made to be like human insulin, but with slight changes to their molecular structures that make them act in certain ways inside the body. For instance, because natural human insulin tends to be limited in how quickly it takes effect and how long its effect lasts, insulin analogs can be engineered to take effect rapidly or to last for a very long time.
Both human insulin and insulin analogs come in vials, prefilled pens, and insulin pumps.
Another important way insulin treatments are categorized is by:
- Onset: How quickly they start working
- Peak: When the effects are strongest
- Duration: How long their effects continue to work
There are six different types of insulin:
Rapid-acting human insulin analogs take effect within 15-20 minutes and reach their peak after an hour, with action lasting 2 to 4 hours.* Some rapid-acting insulin brands include:
- Afrezza (insulin inhaled)
- Apidra (insulin glulisine)
- Humalog (insulin lispro)
- Novolog (insulin aspart)
Regular insulin is available as short-acting human insulin treatment available under a variety of brand names. It takes about 30 minutes to start acting and reaches peak affect at 2 to 3 hours and continues to act for 3 to 6 hours.* Some short-acting insulin brands include:
- Humulin R (insulin normal)
- Novolin R (insulin normal)
Intermediate-acting insulin treatments include both regular human insulin and insulin analog products. It starts working within 1-2 hours and reaches its peak level around 4-12 hours and stays effective for about 12-18 hours.* Some intermediate-acting insulin brands include:
- Humulin N (insulin neutral protamine Hagedorn (NPH))
- Novolin N (insulin neutral protamine Hagedorn (NPH))
Long-acting insulin treatments starts working within 2 to 4 hours and can last in the body for up to 24 hours.* Some long-acting insulin brands include:
- Basaglar (insulin glargine)
- Lantus (insulin glargine)
- Levemir (insulin detemir)
- Toujeo (insulin glargine)
Ultra long-acting insulin has a prolonged release that provides steady insulin in the body for up to 42 hours.* Ultra long-acting insulin brands include:
- Tresiba® (insulin degludec injection)
*The times listed for onset, peak and duration of action are the usual values, however, these values can be highly variable for each patient.
Pre-mixed insulin treatments provide a mix of different insulins to better achieve your blood glucose goals. For example, many people with diabetes will take an intermediate- or long-acting insulin to provide general control throughout the day and then use a rapid- or short-acting insulin around mealtime to cover the boost of carbohydrates that we get with meals. This mixing and matching of insulin treatments allows more tight control of blood glucose and can be tailored to an individual patient’s needs.5
Pre-mixed insulin brands include:
- Humalog Mix 50/50 (50% insulin lispro protamine suspension and 50% insulin lispro injection)
- Humalog Mix 75/25 (75% insulin lispro protamine suspension and 25% insulin lispro injection)
- Humulin 70/30 (70% human insulin isophane suspension and 30% human insulin injection [rDNA origin])
- Novolin 70/30 (70% NPH, human insulin isophane suspension and 30% regular, human insulin injection (recombinant DNA origin))
- Novolog Mix 70/30 (70% insulin aspart protamine suspension and 30% insulin aspart injection (rDNA origin))
All the above mentioned types of insulin treatments are marketed in the US and abroad.
What is basal versus bolus insulin?
Intermediate-, long-, and ultra long-acting insulins are generally referred to as basal insulin treatments (this just means “base therapy”). These are typically injected once or twice daily to achieve a steady base insulin level in the body. The goal of these insulin treatments is to suppress glucose production by the liver (the liver converts glucose stored in the form of glycogen back to glucose) and keeps blood glucose levels within the normal range between meals. Basal levels of insulin can also be achieved with continuous infusion of rapid- or short-acting insulin, but typically basal insulin levels are maintained using intermediate- and long-acting insulin treatments. Short- and rapid-acting insulin are sometimes called bolus insulin treatments because they are given in a bolus injection (the word “bolus” just means a small amount of something). Bolus injections supply the quick-acting insulin you need to process carbohydrates during mealtime. Bolus insulin is typically given just before (5-30 minutes) before a meal.5
What are the regimens of insulin therapy?
Insulin treatment regimens vary in intensity (the number and frequency of injections), depending on the needs of the individual. For some people, an insulin treatment approach involving multiple daily injections may be effective in providing glycemic control. For others, a treatment approach involving fewer daily injections may be more effective. While, still others may need a continuous infusion of insulin (insulin pump). Your healthcare provider will work with you to determine the best insulin treatment approach for you.
What are the different ways of taking insulin?
Taking insulin can be intimidating for many people. This is especially true if you are using intensive insulin therapy to control your blood glucose. Intensive therapy will require frequent injections of insulin. To be successful, you will have to coordinate your daily activities, including meals and exercise, and build in time to check your blood glucose regularly. Fortunately, many advances have been made in insulin delivery methods, making insulin therapy less difficult than in the past and a great option to manage type 2 diabetes.
An important part of making insulin therapy work is staying motivated. Talk to your healthcare provider. Your provider is there to help you with treatment decisions and motivation. You can also reach out to the American Diabetes Association (ADA) for advice and support (1-800-342-2383; www.diabetes.org).
Insulin is typically given as an injection just below the skin (not into the muscle). This kind of shallow injection is called a subcutaneous (SC) injection (SC literally mean “under the skin”). You don’t want to inject too deeply, because you’ll inject insulin into a muscle where it will be absorbed too quickly. You don’t want your injection to go too shallow under the skin because this can be painful and your body won’t absorb the insulin. Your healthcare provider and your certified diabetes educator will help train you to give yourself an SC injection. You can also have your family members and/or friends trained, too.
In addition to injecting yourself at the proper depth, you must also inject yourself at the proper angle. The angle will depend on the location of your injection, your body type, and the type of needle you are using. Since there are many different sizes and kinds of needles and syringes (including pre-filled pens), you should get specific instructions on the use of these from your healthcare provider and from the literature that comes from the manufacturer.
Insulin pumps are small computerized devices that deliver insulin continuously in small doses (‘basal’ insulin) or at your direction as a ‘bolus’ dose, usually around mealtime or if you need a correction or supplemental dose. Insulin doses are delivered through a flexible plastic tube called a catheter, which is inserted through the skin, with the help of a small needle, into the fatty tissue and is taped in place. The pump itself can either be placed in a case or it can be attached to your clothing such as a waistband, belt, pocket or underwear. Your healthcare provider and your certified diabetes educator will help train you to use the pump.
- Mantzoros C. Insulin resistance: Definition and clinical spectrum. Nathan DM, Mulder JE, eds. UptoDate. Wolters Kluwer Health. Accessed at: www.uptodate.com. 2013.
- Inzucchi SE, Bergenstal RM, Buse JB, et al. Management of hyperglycemia in type 2 diabetes: a patient-centered approach: position statement of the American Diabetes Association (ADA) and the European Association for the Study of Diabetes (EASD). Diabetes Care 2012;35:1364-79.
- McCulloch DK. Patient information: Diabetes mellitus type 2: Treatment (Beyond the Basics). Nathan DM, Mulder JE, eds. UptoDate. Wolters Kluwer Health. Accessed at: www.uptodate.com. 2013.
- American Diabetes Association. Pharmacologic approaches to glycemic treatment. Sec. 8. In Standards of Medical Care in Diabetes – 2017. Diabetes Care 2017; 40(Suppl. 1):S64–S74.
- McCulloch DK. General principles of insulin therapy in diabetes mellitus. Nathan DM, Mulder JE, eds. UptoDate. Wolters Kluwer Health. Accessed at: www.uptodate.com. 2014.
- Apidra (insulin glulisine [rDNA origin] injection). Sanofi-Aventis U.S. LLC. Bridgewater, NJ. October 2013.
- NovoLog (insulin aspart [rDNA origin] injection) Prescribing Information. Novo Nordisk Inc. Plainsboro, NJ. January 2013.