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TYPE 1 DIABETES OVERVIEW — Type 1 diabetes mellitus is a chronic medical condition that occurs when the pancreas, an organ in the abdomen, produces very little or no insulin (figure 1). Insulin is a hormone that helps the body to use glucose for energy. Glucose is a sugar that comes, in large part, from foods we eat. Insulin allows glucose to enter cells in the body where it is needed and stores excess glucose for later use. It has other important actions as well. Without insulin, blood glucose (sugar) levels become too high, and over time, this will harm the body.
Type 1 diabetes requires regular blood sugar monitoring and treatment with insulin. Treatment, lifestyle adjustments, and self-care can control blood sugar levels and minimize the risk of disease-related complications.
Type 1 diabetes often begins in childhood or young adulthood, but it can develop at any age. In the United States, Canada, and Europe, type 1 diabetes accounts for 5 to 10 percent of all cases of diabetes.
Other topics that discuss type 1 diabetes are available:
●(See "Patient education: Type 1 diabetes: Insulin treatment (Beyond the Basics)".)
●(See "Patient education: Blood glucose monitoring in diabetes (Beyond the Basics)".)
●(See "Patient education: Type 1 diabetes and diet (Beyond the Basics)".)
●(See "Patient education: Hypoglycemia (low blood glucose) in people with diabetes (Beyond the Basics)".)
DIABETES CARE DURING THE COVID-19 PANDEMIC — COVID-19 stands for "coronavirus disease 2019." It is an infection caused by a virus called SARS-CoV-2. The virus first appeared in late 2019 and has since spread throughout the world.
People with certain underlying health conditions, including diabetes, are at increased risk of severe illness if they get COVID-19. COVID-19 infection can also lead to severe complications of diabetes, including diabetic ketoacidosis (DKA). Getting vaccinated is the best way to lower the risk of severe illness.
THE IMPACT OF TYPE 1 DIABETES — Being diagnosed with type 1 diabetes can be a frightening and overwhelming experience, and it is common to have questions about why it developed, what it means for long-term health, and how it will affect everyday life.
For most people, the first few months after being diagnosed are filled with emotional highs and lows. You and your family can use this time to learn as much as possible so that diabetes-related care (eg, blood glucose [sugar] testing, continuous glucose monitoring, medical appointments, daily insulin, nutrition, foot care) becomes a part of your routine. (See "Patient education: Blood glucose monitoring in diabetes (Beyond the Basics)" and "Patient education: Preventing complications from diabetes (Beyond the Basics)".)
In addition, you should talk with members of your diabetes health care team about resources that are available for medical as well as psychological support. This might include group classes; meetings with a nutritionist, social worker, or nurse educator; and other educational resources, such as books, websites, or magazines. Several of these resources are listed below. (See 'Where to get more information' below.)
Despite the risks associated with type 1 diabetes, most people can lead active lives and continue to enjoy the foods and activities they enjoyed before being diagnosed with diabetes. Diabetes does not mean an end to special occasion foods like birthday cake. With a little advanced planning, most people with diabetes can enjoy exercise in almost any form.
TYPE 1 DIABETES CAUSES — Type 1 diabetes usually develops when the immune system destroys the insulin-producing cells (called the beta cells) in the pancreas. This is called an autoimmune response. The cause of this abnormal immune response is being studied.
This process occurs over many months or years, and there may be no symptoms of diabetes. High blood sugar and its associated symptoms (frequent urination, thirst) do not usually occur until more than 90 percent of the cells that make insulin have been destroyed.
Type 1 diabetes can develop in people with a family history of type 1 diabetes, but it also develops in people with no family history of diabetes. In either case, people who develop diabetes have one or more genes that make them susceptible to the disease. Environmental factors and exposure to certain viruses might trigger the autoimmune response.
Close relatives (children, siblings) of a person with type 1 diabetes have an increased risk of developing type 1 diabetes, compared with a person with no family history (5 to 6 percent versus 0.4 percent, respectively). Genetic testing can help to determine if a family member is at risk of developing diabetes. However, these tests are currently only available to people who participate in a clinical research trial.
Family members at greatest risk for developing type 1 diabetes have high levels of substances called "pancreatic autoantibodies" circulating in their blood, which can indicate that the body has started to destroy its own insulin-producing cells. These blood tests are not routinely obtained, but they are measured in research programs. One such program available across the United States is called TrialNet (www.trialnet.org/our-research/risk-screening).
TYPE 1 DIABETES DIAGNOSIS — The diagnosis of diabetes is based on your symptoms and blood tests.
Symptoms — Most people with type 1 diabetes have symptoms of high blood sugar levels (hyperglycemia) at the time of diagnosis. These include:
●Excessive thirst
●Feeling tired
●Needing to urinate frequently
●Blurred vision
●Feeling hungry
●Unintentional weight loss
●Frequent yeast infections or urinary tract infections
●Slowly healing wounds
Less commonly, there are symptoms of a serious problem called diabetic ketoacidosis (DKA). People with DKA have symptoms of high blood sugar (see above), as well as nausea and vomiting, belly pain, breathing rapidly, feeling sluggish, having trouble paying attention, and sometimes coma. DKA is a medical emergency and must be treated promptly.
Blood tests — Simple, inexpensive blood tests are used to diagnose diabetes. Having a higher than normal blood sugar, as well as the symptoms described above, usually means that you have diabetes.
Type 1 versus type 2 diabetes — In youth, it is usually easy for a health care provider to tell if you have type 1 or type 2 diabetes. In this situation, your health care team will treat you as if you have type 1 while awaiting the results of further blood tests. However, with adult-onset type 1 diabetes, there are many situations where it is not clear if the person has type 1 or 2 diabetes. In this situation, additional blood testing may be ordered.
TYPE 1 DIABETES TREATMENT — Treatment of diabetes requires a team approach, including you and your family and health care providers (doctor, nurse, diabetes educator, dietitian), and sometimes other clinicians (mental health professionals, podiatrist, etc). The treatment of type 1 diabetes is discussed separately. (See "Patient education: Type 1 diabetes: Insulin treatment (Beyond the Basics)".)
COMPLICATIONS OF TYPE 1 DIABETES — Keeping your blood sugar near normal can reduce your risk of long-term complications, such as eye and kidney diseases and problems with the nerves in different parts of your body. This means that you will need to check your blood sugar several times per day or use a continuous glucose monitoring device, give insulin shots or use an insulin pump, monitor what you eat, and see your diabetes care team on a regular basis. You should also have your eyes checked by an eye care professional and practice good foot care (see "Patient education: Foot care for people with diabetes (Beyond the Basics)"). Your diabetes care provider will check your kidney function regularly.
People with type 1 diabetes are at increased risk of cardiovascular disease, which can cause heart attack, chest pain, stroke, and even death. (See "Patient education: Preventing complications from diabetes (Beyond the Basics)".)
However, you can substantially lower your risk of cardiovascular disease by:
●Not smoking (see "Patient education: Quitting smoking (Beyond the Basics)")
●Managing high blood pressure and high cholesterol with diet, exercise, and medications (see "Patient education: High cholesterol and lipids (Beyond the Basics)" and "Patient education: High blood pressure treatment in adults (Beyond the Basics)")
●Keeping your glycated hemoglobin (A1C) at 7 percent or lower
●Taking a low-dose aspirin every day (for adults with cardiovascular disease and sometimes those who are at increased risk of cardiovascular disease)
PREGNANCY AND TYPE 1 DIABETES — Women with type 1 diabetes are usually able to become pregnant and have a healthy baby. However, it is important to carefully control blood sugar levels before and during pregnancy to minimize the risk of complications. A full discussion of this topic is available separately. (See "Patient education: Care during pregnancy for patients with type 1 or 2 diabetes (Beyond the Basics)".)
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 1 diabetes (The Basics)
Patient education: Hemoglobin A1C tests (The Basics)
Patient education: Preparing for pregnancy when you have diabetes (The Basics)
Patient education: Diabetic ketoacidosis (The Basics)
Patient education: Friedreich ataxia (The Basics)
Patient education: Diabetes and infections (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 1 diabetes: Insulin treatment (Beyond the Basics)
Patient education: Blood glucose monitoring in diabetes (Beyond the Basics)
Patient education: Type 1 diabetes and diet (Beyond the Basics)
Patient education: Hypoglycemia (low blood glucose) in people with diabetes (Beyond the Basics)
Patient education: Care during pregnancy for patients with type 1 or 2 diabetes (Beyond the Basics)
Patient education: Preventing complications from diabetes (Beyond the Basics)
Patient education: Quitting smoking (Beyond the Basics)
Patient education: High cholesterol and lipids (Beyond the Basics)
Patient education: High blood pressure treatment in adults (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.
Amylin analogs for the treatment of diabetes mellitus
Glucose monitoring in the ambulatory management of nonpregnant adults with diabetes mellitus
Classification of diabetes mellitus and genetic diabetic syndromes
Clinical presentation, diagnosis, and initial evaluation of diabetes mellitus in adults
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 1 diabetes mellitus
Pregestational (preexisting) diabetes mellitus: Antenatal glycemic control
Pancreatic beta cell function
Management of blood glucose in adults with type 1 diabetes mellitus
Hypoglycemia in adults with diabetes mellitus
Moderately increased albuminuria (microalbuminuria) in type 1 diabetes mellitus
Nutritional considerations in type 1 diabetes mellitus
Diabetic kidney disease: Pathogenesis and epidemiology
Overview of general medical care in nonpregnant adults with diabetes mellitus
Pancreas and islet transplantation in diabetes mellitus
The following organizations also provide reliable health information.
●National Library of Medicine
(www.nlm.nih.gov/medlineplus/healthtopics.html)
●National Institute of Diabetes and Digestive and Kidney Diseases
●American Diabetes Association (ADA)
(800)-DIABETES (800-342-2383)
●The Endocrine Society
●Hormone Health Network
(www.hormone.org/diseases-and-conditions/diabetes, available in English and Spanish)
●Juvenile Diabetes Research Foundation
●Glu, an online community of the T1D Exchange
●US Centers for Disease Control and Prevention
(www.cdc.gov/diabetes/basics/type1.html, available in English and Spanish)
●Type 1 Diabetes TrialNet: Pathway to Prevention
