Last week, we started to take a closer look at insulin, a hormone that helps to lower blood sugar levels and a hormone that everyone needs. Insulin works much like a key, unlocking receptors that are located on cells, allowing glucose to enter and be used for energy. When the pancreas works as it should, insulin helps to regulate, or balance out, blood sugar levels. If there is more sugar in the blood than the body currently needs, the sugar gets stored in the liver as glycogen (or, if glycogen stores are full, as fat). Then, when the body needs more sugar, say, for physical activity, the liver will release glucose to provide additional fuel for the body.
Types of insulin
If you have Type 1 diabetes, you very likely take two types of insulin: rapid-acting or short-acting, also known as mealtime or bolus insulin, and longer-acting, also known as basal insulin. People who have Type 2 diabetes may take just one type or both types.
Rapid-acting insulin. This type of insulin starts to work about 15 minutes after you inject it. It will peak about 1 hour later, but it keeps working for 2 to 4 hours. Rapid-acting insulin is generally taken right before eating a meal to “cover” the carbohydrate consumed at that meal. Rapid-acting insulin is generally the only type of insulin used in an insulin pump (longer-acting insulins are never used in a pump).
Examples: aspart (brand name NovoLog), lispro (Humalog), glulisine (Apidra)
Short-acting insulin. Also a type of mealtime insulin, short-acting insulin is taken about 30 minutes before a meal. It starts to work about 30 minutes after injecting, peaks 2–5 hours later, and lasts up to 12 hours. With the newer rapid-acting insulins now available that offer more flexibility, short-acting insulin isn’t used as much as it used to be.
Examples: regular insulin (Humulin R, Novolin R, ReliOn R)
Intermediate-acting insulin. Intermediate-acting insulin starts to work about 1 1/2 to 4 hours after injection, peaks between 4 and 12 hours later, and can last up to 24 hours in some people. This type of insulin is usually taken twice a day, in the morning and at dinnertime or bedtime.
Examples: NPH insulin (Humulin N, Novolin N, ReliOn N)
Long-acting insulin. Long-acting insulin, often called basal insulin, helps to keep blood sugar levels more stable overnight and between meals. This type of insulin starts to work several hours after it’s injected. There is a minimal peak with this insulin, however. It’s supposed to last up to 24 hours, although many people find that it doesn’t last that long. Long-acting insulin may be taken once or twice a day. An exception to this is a brand-new long-acting insulin that hit the market this past spring, called Toujeo. This insulin is taken once a day and is supposedly designed to truly last 24 hours. And just this past week, the FDA approved another long-acting insulin called Tresiba, designed to last at least 42 hours! Long-acting insulin can never be mixed in the same syringe with other types of insulin; this means that two separate injections are needed if you need both long-acting and rapid- or short-acting insulin.
Examples: glargine (Lantus, Toujeo), detemir (Levemir), degludec (Tresiba)
Inhaled insulin. The above-mentioned insulins must all be injected with a syringe or insulin pen, or administered via an insulin pump. A new insulin, called Afrezza, is inhaled. Afrezza is a powdered form of insulin that comes in cartridges. The cartridge is placed inside an inhaler that’s about the size of a whistle. Afrezza is a mealtime, or ultra-rapid-acting, insulin. If a person also requires long-acting insulin, he must still take that by injection. This insulin begins working within 12–15 minutes of inhaling it, peaks at about 30 minutes, and lasts for about 3 hours.
Premixed insulin. Premixed insulin is available for people who need or desire a simplified insulin regimen, such as people who are older, who have limited dexterity, or who have impaired vision, for example. Premixed insulin can also be suitable for someone who is new to insulin and is feeling overwhelmed with taking multiple injections every day. This type of insulin is a combination of NPH (intermediate-acting insulin) and a rapid- or short-acting insulin.
70/30: 70% NPH, 30% regular
50/50: 50% NPH, 50% regular
75/25: 75% NPH, 25% lispro
70/30: 70% NPH, 30% aspart
Premixed insulins peak within about 15–30 minutes after injection (depending on the type) and generally last between 10–16 hours, though they may last up to 24 hours. Premixed insulins sound ideal in that taking one of these can decrease the number of injections a person may have to take. However, the drawback is that while the dose can be adjusted, the ratio of long-acting to rapid-acting cannot; increasing or decreasing the dose changes both amounts of insulin. Fine-tuning, therefore, is often not possible with premixed insulins.
There are obviously a lot of options available when it comes to taking insulin. Talk with your health-care team about what type of insulin is right for you. As I mentioned earlier, people who are newly diagnosed with Type 1 diabetes will need a fast-acting (bolus) and longer-acting (basal) insulin. People who have Type 2 diabetes who need insulin often start off with a basal insulin, and then, perhaps, eventually add a fast-acting insulin. The newer insulins, called insulin analogs, are popular because they allow you to be flexible in terms of when you inject the insulin, as well as when and how much you eat. On the other hand, insulin analogs are more expensive than the human insulins (regular and NPH), so cost and health-plan coverage is definitely a consideration, too. Learn about the different types of insulin so that you can have a healthy and informed conversation with your doctor.
More on insulin next week!
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Amy Campbell: Amy Campbell is the author of Staying Healthy with Diabetes: Nutrition and Meal Planning and a frequent contributor to Diabetes Self-Management and Diabetes & You. She has co-authored several books, including the The Joslin Guide to Diabetes and the American Diabetes Association’s 16 Myths of a “Diabetic Diet,” for which she received a Will Solimene Award of Excellence in Medical Communication and a National Health Information Award in 2000. Amy also developed menus for Fit Not Fat at Forty Plus and co-authored Eat Carbs, Lose Weight with fitness expert Denise Austin. Amy earned a bachelor’s degree in nutrition from Simmons College and a master’s degree in nutrition education from Boston University. In addition to being a Registered Dietitian, she is a Certified Diabetes Educator and a member of the American Dietetic Association, the American Diabetes Association, and the American Association of Diabetes Educators. Amy was formerly a Diabetes and Nutrition Educator at Joslin Diabetes Center, where she was responsible for the development, implementation, and evaluation of disease management programs, including clinical guideline and educational material development, and the development, testing, and implementation of disease management applications. She is currently the Director of Clinical Education Content Development and Training at Good Measures. Amy has developed and conducted training sessions for various disease and case management programs and is a frequent presenter at disease management events.
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