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TYPE 2 DIABETES OVERVIEW — Type 2 diabetes mellitus is a disorder that is known for disrupting the way your body uses glucose (sugar); it also causes other problems with the way your body stores and processes other forms of energy, including fat.
All the cells in your body need glucose to work normally. Glucose gets into the cells with the help of a hormone called insulin. In type 2 diabetes, the body stops responding to normal or even high levels of insulin, and over time, the pancreas (an organ in the abdomen) does not make enough insulin to keep up with what the body needs. Being overweight, especially having extra fat stored in the liver and abdomen, increases the body's demand for insulin. This causes glucose to build up in the blood, which can lead to problems if untreated.
People with type 2 diabetes require regular monitoring and ongoing treatment to maintain goal blood sugar levels and, equally importantly, to manage other conditions that go along with diabetes. Treatment includes lifestyle adjustments, self-care measures, and medications (which may or may not include insulin); combined, these approaches can help reduce the risk of complications. Learning to manage diabetes is a process that continues over a lifetime.
This topic review discusses the role of insulin treatment in controlling blood sugar for people with type 2 diabetes. Separate topic reviews about other aspects of type 2 diabetes are also available. (See "Patient education: Type 2 diabetes: Overview (Beyond the Basics)" and "Patient education: Blood glucose monitoring in diabetes (Beyond the Basics)" and "Patient education: Hypoglycemia (low blood glucose) in people with diabetes (Beyond the Basics)" and "Patient education: Type 2 diabetes: Alcohol, exercise, and medical care (Beyond the Basics)" and "Patient education: Preventing complications from diabetes (Beyond the Basics)" and "Patient education: Type 2 diabetes and diet (Beyond the Basics)".)
IMPORTANCE OF BLOOD SUGAR CONTROL IN TYPE 2 DIABETES — Keeping your blood sugar levels under control is one way to decrease the risk of complications related to type 2 diabetes, particularly microvascular complications. ("Micro" means small, and "vascular" means blood vessels.) These can affect the eyes, kidneys, and nerves; these problems can lead to serious issues including blindness, kidney failure, foot ulcers requiring amputation, and impotence in men. Microvascular complications usually occur after a person has had diabetes for many years, and they are related to elevated levels of blood sugar over time. However, in some cases (eg, if a person has already had diabetes for a long time before they seek medical care), these complications may be present at the time of initial diagnosis.
The most common complication of type 2 diabetes is cardiovascular (heart) disease, also known as macrovascular disease ("macro" means large, ie, affecting the large blood vessels). Heart disease increases a person's risk of heart attack and death. There are ways to lower your risk of heart disease, including lifestyle changes (such as avoiding smoking, eating a healthy diet, exercising regularly, and maintaining a healthy weight) and medications to control blood pressure and cholesterol, if needed. Specific diabetes drugs also help reduce the risk of cardiovascular disease in people with or at high risk for cardiovascular disease. (See "Patient education: Preventing complications from diabetes (Beyond the Basics)".)
Monitoring — Many people with type 2 diabetes need to check their blood sugar regularly. This is especially important for people who use insulin or other medications that can lower blood sugar levels too much. That's because while high blood sugar (hyperglycemia) can lead to complications, having a blood sugar level that is too low (hypoglycemia) can also cause problems. (See "Patient education: Blood glucose monitoring in diabetes (Beyond the Basics)".)
Blood sugar control is often measured by checking the level before your first meal of the day (fasting). A normal fasting blood sugar is typically less than 100 mg/dL (5.6 mmol/L), although different people will have a different goal; an example might be 80 to 130 mg/dL (4.4 to 7.2 mmol/L). Your health care provider can work with you to determine what your goal should be. Some people need to test their blood sugar level before and/or after other meals during the day. The frequency of testing and blood sugar goals can change over time, so it's important to see your health care provider regularly. (See 'How often to see your provider' below.)
Blood sugar control can also be measured with a blood test called A1C. The A1C blood test is an indicator of your average blood sugar level over the past two to three months. Knowing your average level can be useful as blood sugar levels can fluctuate throughout the day depending on your diet and activity level. The A1C test involves having a blood sample taken (either from a vein or through a finger prick) in a doctor's office for testing. The goal A1C for most people with type 2 diabetes is less than 7 percent, which corresponds to an average blood sugar of 154 mg/dL (8.6 mmol/L) (table 1). However, different people have different goals for what their A1C level should be. For example, people who are older or have several other medical conditions might have a slightly higher goal. Your health care provider will work with you to understand your A1C goal.
The A1C measures the amount of blood sugar that is stuck to hemoglobin, a molecule in red blood cells. Sometimes, the A1C cannot accurately measure average blood sugar; this can be due to conditions that affect red blood cells or normal variations in how long the red blood cells last in the body. If your health care provider suspects that your A1C results are inaccurate, they may use other methods to measure your blood sugar level.
How often to see your provider — Most people with type 2 diabetes meet with their health care provider every three to four months. At these visits, you will discuss your blood sugar and other care goals and how you are managing your diabetes, including your medications. This allows you and your provider to work together to fine-tune your care plan and keep you as healthy as possible.
STARTING INSULIN — Most people who are newly diagnosed with type 2 diabetes begin initial treatment with a combination of diet, exercise, and an oral (pill or tablet) medication. Over time, some people will need to add insulin or another injectable medication because their blood sugar levels are not well managed with oral medication. In some cases, insulin (or another injectable medication) is recommended first, as initial treatment. Your health care provider will talk to you about your options and goals, and work with you to make a treatment plan.
Types of insulin — There are several types of insulin. These types are classified according to how quickly the insulin begins to work and how long it remains active:
●Rapid acting, eg:
•Insulin lispro (sample brand names: Admelog, Humalog, Lyumjev)
•Insulin aspart (brand names: Fiasp, NovoLog)
•Insulin glulisine (brand name: Apidra)
●Short acting, eg, insulin regular (brand name: Humulin R)
●Intermediate acting, eg:
•Insulin NPH (brand name: Humulin N)
•Insulin isophane suspension (mixed with human insulin [brand name: Humulin 70/30])
•Insulin lispro protamine (mixed with rapid-acting insulin lispro [brand name: Humalog Mix 75/25 or 50/50])
•Insulin aspart protamine (mixed with rapid-acting aspart [brand name: Novolog Mix])
●Long acting, eg:
•Insulin glargine (brand name: Basaglar, Lantus)
•Insulin detemir (brand name: Levemir; intermediate to long acting; may be needed twice daily)
●Very long acting, eg:
•Insulin degludec (brand name: Tresiba)
•Insulin glargine 300 units/mL (brand name: Toujeo)
One form of inhaled insulin (brand name: Afrezza) is available in the United States. Inhaled insulin has not been shown to lower A1C levels to the usual target level of less than 7 percent in most studies. In addition, lung function testing is required before starting it and periodically during therapy. For these reasons, inhaled insulin has not been used widely.
Initial insulin dose — When insulin is started for type 2 diabetes, health care providers usually recommend "basal" insulin; this means taking intermediate-acting and/or long-acting forms of insulin to keep blood sugar controlled throughout the day. You will likely need to take basal insulin once per day, either in the morning or at bedtime.
If you are using a combination of treatments (ie, an oral medication plus insulin), it generally means that you can take a lower dose of insulin compared with people who take insulin only. Since insulin can cause weight gain, combination therapy may reduce your risk of weight gain. Your health care provider will work with you to monitor your body's response and adjust the dose over time.
Adjusting insulin dose over time — To determine how and when to adjust your once-daily insulin dose, you will need to measure your blood sugar level every morning before eating. If the value is consistently higher than your fasting blood sugar goal, and you do not have episodes of low blood sugar (especially overnight), your provider may recommend increasing your insulin dose. (See "Patient education: Blood glucose monitoring in diabetes (Beyond the Basics)".)
If the initial insulin regimen is still not adequately controlling your blood sugar levels, your health care provider might recommend giving yourself two injections a day, depending on the type of insulin you use. Being diagnosed with a new medical problem or requiring a new medication can also change the body's needs for insulin, sometimes requiring a change in diabetes treatment. For example, when a person with type 2 diabetes takes steroids (eg, prednisone) for an asthma attack or other reasons, the blood sugar levels increase. This usually requires temporarily increasing the dose of insulin.
Type 2 diabetes typically progresses over time, causing the body to produce less insulin. Some people will need a more complex insulin regimen. In this situation, a pre-meal (prandial) dose of rapid-acting or short-acting insulin is added to the once-daily dose of basal insulin. As a first step, prandial insulin may be started as a single injection before the largest meal of the day, but your health care provider might suggest another approach. The dose of short-acting or rapid-acting insulin is adjusted immediately prior to a meal; the dose needed depends on many different factors, including your current and goal blood sugar level, the carbohydrate content of the meal, and your activity level.
People with type 2 diabetes are occasionally treated with "intensive" insulin regimens. Intensive insulin treatment requires multiple injections of insulin per day or the use of an insulin pump. It also requires measuring blood sugar levels several times a day, with adjustment of pre-meal insulin dosing based on the size and carbohydrate content of the meal. This approach is more commonly used in people with type 1 diabetes, and it is discussed in greater detail in a separate topic review. (See "Patient education: Type 1 diabetes: Insulin treatment (Beyond the Basics)", section on 'Intensive insulin treatment'.)
INJECTING INSULIN — Insulin cannot be taken in pill form. It is usually injected into the layer of fat under the skin (called "subcutaneous" injection) with a device called a "pen injector" or a needle and syringe.
You can inject insulin into different areas of your body (figure 1). You will need to learn how to use an insulin pen injector or, if you use a needle and syringe, draw up and inject your insulin. You may also want to have your partner or a family member learn how to give insulin shots. The site and the insulin dose determine how quickly the insulin is absorbed. (See 'Site of injection' below.)
Insulin pen injectors — Insulin pen injectors may be more convenient to carry and use, particularly when you are away from home. Most are approximately the size of a large writing pen and contain a cartridge that contains the insulin, a dial to set the dose, and a button to deliver the injection (figure 2). A new needle must be attached to the pen prior to each injection. The needles are sold separately from the pens. Insulin pen cartridges should never be shared, even if the needle is changed. The injection technique is similar to using a needle and syringe. (See 'Injection technique' below.)
Pens are especially useful for accurately injecting very small doses of insulin and may be easier to use if you have vision problems. Pens are more expensive than traditional syringes and needles. A number of different insulin pens are available; if your health care provider prescribes a pen for you, it will come with specific instructions for use.
Needle and syringe — Some people use a needle and syringe (rather than a pen injector) to give themselves insulin. This involves drawing up insulin from a bottle using the syringe, then injecting it with the needle.
Drawing up insulin — There are many different types of syringes and needles, so it's best to get specific instructions for drawing up insulin from a health care provider. The basic steps are listed in the table (table 2). People who use an insulin pen rather than a syringe should follow the instructions provided by the pen manufacturer and their health care provider. (See 'Insulin pen injectors' above.)
Before drawing up insulin, it is important to know the dose and type of insulin needed; if you use more than one type of insulin, you will need to calculate the total dose needed (your health care provider will show you how to do this). Some people, including children and those with vision problems, may need assistance. Magnification and other assistive devices are available. If you have difficulty drawing up your insulin, let your health care provider know, as there are ways to help with this.
One type of insulin, called U-500 insulin, requires a special U-500 syringe; this syringe makes it easier to measure the right dose. If you use this type of insulin, your health care provider can show you how to use the U-500 syringe. It's very important to use this specially marked syringe only for U-500 insulin. Using a U-500 syringe with other insulins can cause a dangerous insulin overdose. Because it can be confusing to figure out how to accurately measure the correct dose, U-500 insulin and other concentrated insulins (U-200 lispro or degludec) should be prescribed in an insulin pen device. (See 'Insulin pen injectors' above.)
Injection angle — Insulin is usually injected under the skin (figure 3). It is important to use the correct injection angle since injecting too deeply could deliver insulin to the muscle, where it is absorbed too quickly. On the other hand, injections that are too shallow are more painful and not absorbed well.
The best angle for insulin injection depends on your body type, injection site, and length of the needle used. Your health care provider can help you figure out what length needle to use and the angle at which to inject your insulin.
Injection technique — These are the basic steps for injecting insulin:
●Choose the site to inject (figure 1). You do not need to clean the skin with alcohol unless your skin is dirty.
●Pinch up a fold of skin and quickly insert the needle at a 90° angle (or the angle you have discussed with your provider, if it is different) (figure 3). Keep the skin pinched to avoid injecting insulin into the muscle.
●Push the plunger down completely to inject the insulin. Hold the syringe and needle in place for 5 seconds for syringes and 10 seconds for insulin pens.
●Release the skin.
●Remove the needle from the skin.
If you see blood or clear fluid (insulin) at the injection site, apply pressure to the area for a few seconds. Do not rub the skin, as this can cause the insulin to be absorbed too quickly.
Each needle and syringe should be used once and then thrown away; needles become dull quickly, potentially increasing the pain of injection. Needles and syringes should never be shared. Used needles and syringes should not be included with regular household trash but should instead be placed in a puncture-proof container (eg, a hard laundry detergent bottle) or a sharps container, which is available from most pharmacies or hospital supply stores.
FACTORS AFFECTING INSULIN ACTION — Several factors can affect how injected insulin works.
Dose of insulin injected — The dose of insulin injected affects the rate at which the body absorbs it. Larger doses of insulin may be absorbed more slowly than smaller doses.
Site of injection — It is very important to rotate injection sites (ie, avoid using the same site each time) to minimize tissue irritation or damage. When changing sites, it is important to keep in mind that insulin is absorbed at different rates in different areas of the body.
Insulin is absorbed fastest from the abdominal area, slowest from the leg and buttock, and at an intermediate rate from the arm. This may vary with the amount of fat present; areas with more fat under the skin absorb insulin more slowly (figure 1).
It is reasonable to use the same general area for injections given at the same time of the day. Sometimes abdominal injections, which are absorbed more quickly, are preferred before meals. Injection into the thigh or buttock may be best for the evening dose because the insulin will be absorbed more slowly during the night.
Smoking and physical activity — Any factors that alter the rate of blood flow through the skin and fat will change insulin absorption. Smoking decreases blood flow, which in turn decreases insulin absorption. In contrast, activities that increase blood flow (such as exercise, saunas, hot baths, and massaging the injection site) increase insulin absorption and can result in hypoglycemia (low blood sugar). For these reasons, it is best to avoid injecting your insulin immediately after any of these activities. Your health care provider might also recommend taking a lower dose of insulin before or after exercise.
Decreased potency over time — Most insulin remains potent and effective for up to a month after the bottle has been opened (if kept in the refrigerator between injections). However, the potency of intermediate-acting and long-acting insulin begins to decrease after 30 days. This can be a problem for people who require very small doses of insulin, for whom a bottle might last two months or more. If you use a needle and syringe, it is advisable to start a new bottle at least every 30 days.
If you use an insulin pen, it will come with specific instructions about how to store and use the device. Unopened insulin pens are usually stored in the refrigerator. Once the pen is opened, most pen injectors can be kept at room temperature (eg, in a purse or jacket pocket) for up to 14 to 28 days, depending on the type of insulin (premixed insulin loses potency more quickly). It's important to avoid exposing the pen to extreme temperatures (hot or cold). After the specified number of days, or if there is suspicion that the insulin has lost potency (for example, if the pen was left in a hot car), a new insulin cartridge or pen should be used, even if there is insulin left in the old cartridge.
Individual differences — The same dose of the same type of insulin may have different effects in different people with diabetes. Some trial-and-error is usually necessary to find the ideal type(s) and dose of insulin and schedule for each person.
Insulin needs often change over a person's lifetime. Changes in weight, diet, health conditions (including pregnancy), activity level, and occupation can have an impact on the amount of insulin needed to control blood sugar levels. Your health care provider should be able to teach you to adjust your own insulin dose as needed, but this will depend on your specific situation. (See "Patient education: Care during pregnancy for patients with type 1 or 2 diabetes (Beyond the Basics)".)
SPECIAL SITUATIONS — Several situations can complicate insulin treatment for a person with diabetes. With advance planning and careful calculation, these situations are less likely to cause major fluctuations in your blood sugar control. Your health care provider can assist you in handling these situations.
Eating out — Eating out can be challenging since the ingredients used, calorie and fat content, and portion sizes are usually different from meals prepared at home. If your insulin regimen involves injecting the same amount of insulin at the same time each day, being consistent about when and what you eat will help to improve blood sugar control. If meal timing and content varies widely, blood sugar levels will fluctuate as well, making it less likely that you will meet your goal A1C level. When dining out, you can make healthy food choices by requesting nutrition information from the restaurant or referring to a web site, phone app, or reference book. (See "Patient education: Type 2 diabetes and diet (Beyond the Basics)".)
Hypoglycemia and hyperglycemia can occur more easily in situations where you are eating new or different foods; thus, it's important to keep a fast-acting source of carbohydrates (such as hard candy or glucose tablets) as well as a blood glucose monitor with you at all times. (See "Patient education: Hypoglycemia (low blood glucose) in people with diabetes (Beyond the Basics)".)
Surgery — If you need to have surgery or another procedure, you may be instructed not to eat for 8 to 12 hours before their procedure. In this situation, a health care provider can help you determine the dose and timing of insulin to use before and after the procedure. This is particularly important if you will be unable to eat a normal diet for a time afterwards.
Infections — Infections (such as a cold, sore throat, urinary tract infection, or any infection that causes fever) can cause blood sugar levels to rise.
If you get sick, it's a good idea to talk with your health care provider, as you will need to carefully monitor your blood sugar levels and possibly increase your insulin dose. It is also important to drink plenty of fluids in order to avoid dehydration. If you have nausea or vomiting, you may need medication to control your symptoms and avoid dehydration.
Travel — Managing blood sugar levels and insulin treatment while traveling can be difficult, especially if you are traveling across multiple time zones. In addition, activity levels and diet are often different while traveling, making it especially important to carefully monitor your blood sugar levels. If you are planning travel, talk with your health care provider to develop a plan for managing your diabetes. (See "Patient education: General travel advice (Beyond the Basics)", section on 'Traveling with medical conditions'.)
STAYING MOTIVATED WITH TYPE 2 DIABETES — Living with diabetes can be very demanding, and some patients lose motivation over time. Your health care provider can provide tips and encouragement to help you stay on track. Helpful information and support is also available from the American Diabetes Association (ADA) at (800)-DIABETES (800-342-2383) and at www.diabetes.org.
WHERE TO GET MORE INFORMATION — Your health care provider is the best source of information for questions and concerns related to your medical problem.
This article will be updated as needed on our website (www.uptodate.com/patients). Related topics for patients, as well as selected articles written for health care professionals, are also available. Some of the most relevant are listed below.
Patient level information — UpToDate offers two types of patient education materials.
The Basics — The Basics patient education pieces answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials.
Patient education: Type 2 diabetes (The Basics)
Patient education: Using insulin (The Basics)
Patient education: Treatment for type 2 diabetes (The Basics)
Patient education: Low blood sugar in people with diabetes (The Basics)
Patient education: Diabetes and diet (The Basics)
Patient education: Diabetic ketoacidosis (The Basics)
Patient education: Hyperosmolar hyperglycemic state (The Basics)
Patient education: Should I switch to an insulin pump? (The Basics)
Beyond the Basics — Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are best for patients who want in-depth information and are comfortable with some medical jargon.
Patient education: Type 2 diabetes: Overview (Beyond the Basics)
Patient education: Blood glucose monitoring in diabetes (Beyond the Basics)
Patient education: Hypoglycemia (low blood glucose) in people with diabetes (Beyond the Basics)
Patient education: Type 2 diabetes: Alcohol, exercise, and medical care (Beyond the Basics)
Patient education: Preventing complications from diabetes (Beyond the Basics)
Patient education: Type 2 diabetes: Treatment (Beyond the Basics)
Patient education: Type 2 diabetes and diet (Beyond the Basics)
Patient education: Type 1 diabetes: Insulin treatment (Beyond the Basics)
Patient education: Care during pregnancy for patients with type 1 or 2 diabetes (Beyond the Basics)
Patient education: General travel advice (Beyond the Basics)
Professional level information — Professional level articles are designed to keep doctors and other health professionals up-to-date on the latest medical findings. These articles are thorough, long, and complex, and they contain multiple references to the research on which they are based. Professional level articles are best for people who are comfortable with a lot of medical terminology and who want to read the same materials their doctors are reading.
Alpha-glucosidase inhibitors for treatment of diabetes mellitus
Exercise guidance in adults with diabetes mellitus
Measurements of glycemia in diabetes mellitus
General principles of insulin therapy in diabetes mellitus
Glycemic control and vascular complications in type 2 diabetes mellitus
Pregestational (preexisting) diabetes mellitus: Antenatal glycemic control
Inhaled insulin therapy in diabetes mellitus
Initial management of hyperglycemia in adults with type 2 diabetes mellitus
Insulin therapy in type 2 diabetes mellitus
Management of diabetes mellitus in hospitalized patients
Management of persistent hyperglycemia in type 2 diabetes mellitus
Metformin in the treatment of adults with type 2 diabetes mellitus
Overview of general medical care in nonpregnant adults with diabetes mellitus
Sulfonylureas and meglitinides in the treatment of type 2 diabetes mellitus
Thiazolidinediones in the treatment of type 2 diabetes mellitus
The following organizations also provide reliable health information.
●National Library of Medicine
●National Institute of Diabetes and Digestive and Kidney Diseases
●American Diabetes Association (ADA)
●Canadian Diabetes Associates
●Juvenile Diabetes Research Foundation
●US Center for Disease Control and Prevention