Patient information: Diabetes mellitus type 1: Overview (Beyond the Basics)
- David K McCulloch, MD
David K McCulloch, MD
- Clinical Professor of Medicine
- University of Washington
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 absorb and use glucose and other nutrients from food, store fat, and build up protein. Without insulin, blood glucose (sugar) levels become higher than normal.
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 usually begins in childhood or young adulthood, but 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.
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 patients, 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, self-blood sugar testing, medical appointments, daily insulin) becomes a "normal" part of your routine. (See "Patient information: Self-blood glucose monitoring in diabetes mellitus (Beyond the Basics)".)
In addition, you should talk with your doctor or nurse 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, web sites, 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, such as exposure to certain viruses and foods early in life, 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 to 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.
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). This includes:
●Needing to urinate frequently
Less commonly, there are symptoms of a 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 — Several blood tests are used to measure blood sugar levels. 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 — It is usually easy to tell if you have type 1 or type 2 diabetes. However, there are situations where it is not clear if a person has type 1 or 2 diabetes. In this situation, your doctor or nurse will treat you as if you have type 1 while waiting on the results of further blood tests.
TYPE 1 DIABETES TREATMENT
Treatment of diabetes requires a team approach, including you and your family and healthcare providers (doctor, nurse, diabetes educator, dietitian), and sometimes other clinicians (exercise physiologist, podiatrist, etc). The treatment of type 1 diabetes is discussed separately. (See "Patient information: Diabetes mellitus type 1: Insulin treatment (Beyond the Basics)".)
COMPLICATIONS OF TYPE 1 DIABETES
Keeping your blood sugar near-normal can reduce your risk of long-term complications. This means that you will need to check your blood sugar several times per day, give insulin shots or use an insulin pump, monitor what you eat, and see your doctor or nurse on a regular basis.
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 information: Preventing complications in diabetes mellitus (Beyond the Basics)".)
However, you can substantially lower your risk of cardiovascular disease by:
●Not smoking (see "Patient information: Quitting smoking (Beyond the Basics)")
●Taking a low-dose aspirin every day if indicated (for adults only)
●Managing high blood pressure and high cholesterol with diet, exercise, and medications (see "Patient information: High cholesterol and lipids (hyperlipidemia) (Beyond the Basics)" and "Patient information: High blood pressure treatment in adults (Beyond the Basics)")
●Keeping your glycated hemoglobin (A1C) at 7 percent or lower
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 tightly 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 information: Care during pregnancy for women with type 1 or 2 diabetes mellitus (Beyond the Basics)".)
WHERE TO GET MORE INFORMATION
Your healthcare 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 web site (www.uptodate.com/patients). Related topics for patients, as well as selected articles written for healthcare 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 information: Type 1 diabetes (The Basics)
Patient information: Hemoglobin A1C tests (The Basics)
Patient information: Preparing for pregnancy when you have diabetes (The Basics)
Patient information: Diabetic ketoacidosis (The Basics)
Patient information: Friedreich ataxia (The Basics)
Patient information: 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 information: Diabetes mellitus type 1: Insulin treatment (Beyond the Basics)
Patient information: Self-blood glucose monitoring in diabetes mellitus (Beyond the Basics)
Patient information: Type 1 diabetes mellitus and diet (Beyond the Basics)
Patient information: Hypoglycemia (low blood sugar) in diabetes mellitus (Beyond the Basics)
Patient information: Care during pregnancy for women with type 1 or 2 diabetes mellitus (Beyond the Basics)
Patient information: Preventing complications in diabetes mellitus (Beyond the Basics)
Patient information: Quitting smoking (Beyond the Basics)
Patient information: High cholesterol and lipids (hyperlipidemia) (Beyond the Basics)
Patient information: 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
Blood glucose self-monitoring in management of adults with diabetes mellitus
Classification of diabetes mellitus and genetic diabetic syndromes
Clinical presentation and diagnosis of diabetes mellitus in adults
Effects of exercise in diabetes mellitus in adults
Estimation of blood glucose control in diabetes mellitus
General principles of insulin therapy in diabetes mellitus
Glycemic control and vascular complications in type 1 diabetes mellitus
Pregestational diabetes mellitus: Prenatal glycemic control
Insulin secretion and pancreatic beta cell function
Management of blood glucose in adults with type 1 diabetes mellitus
Management of hypoglycemia during treatment of diabetes mellitus
Moderately increased albuminuria (microalbuminuria) in type 1 diabetes mellitus
Nutritional considerations in type 1 diabetes mellitus
Overview of diabetic nephropathy
Overview of medical care in adults with diabetes mellitus
Pancreas and islet transplantation in 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)
●The Endocrine Society
●Hormone Health Network
(www.hormone.org/diseases-and-conditions/diabetes, available in English and Spanish)
- The effect of intensive treatment of diabetes on the development and progression of long-term complications in insulin-dependent diabetes mellitus. The Diabetes Control and Complications Trial Research Group. N Engl J Med 1993; 329:977.
- Alberti KG, Zimmet PZ. Definition, diagnosis and classification of diabetes mellitus and its complications. Part 1: diagnosis and classification of diabetes mellitus provisional report of a WHO consultation. Diabet Med 1998; 15:539.
- Report of the Expert Committee on the Diagnosis and Classification of Diabetes Mellitus. Diabetes Care 1997; 20:1183.
- Nathan DM, Cleary PA, Backlund JY, et al. Intensive diabetes treatment and cardiovascular disease in patients with type 1 diabetes. N Engl J Med 2005; 353:2643.
- Retinopathy and nephropathy in patients with type 1 diabetes four years after a trial of intensive therapy. The Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications Research Group. N Engl J Med 2000; 342:381.
- LaGasse JM, Brantley MS, Leech NJ, et al. Successful prospective prediction of type 1 diabetes in schoolchildren through multiple defined autoantibodies: an 8-year follow-up of the Washington State Diabetes Prediction Study. Diabetes Care 2002; 25:505.
All topics are updated as new information becomes available. Our peer review process typically takes one to six weeks depending on the issue.