Diabetes mellitus type 1

Diabetes mellitus is a lifelong condition that can be controlled with lifestyle adjustments and medical treatments. Keeping blood sugar levels under control can prevent or minimize complications. Insulin treatment is one component of a diabetes treatment plan for people with type 1 diabetes.

Insulin treatment replaces or supplements the body's own insulin, restoring normal or near-normal blood sugar levels. Many different types of insulin treatment can successfully control blood sugar levels; the best option depends upon a variety of individual factors. With a little extra planning, people with diabetes who take insulin can lead a full life and keep their blood sugar under control.

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.


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.

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.

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 can occur at any age. It is most often diagnosed in children, adolescents, or young adults.

Insulin is a hormone produced in the pancreas by special cells called beta cells. The pancreas is below and behind the stomach. Insulin is needed to move blood sugar (glucose) into cells. Inside the cells, glucose is stored and later used for energy. With type 1 diabetes, beta cells produce little or no insulin.

Without enough insulin, glucose builds up in the bloodstream instead of going into the cells. This buildup of glucose in the blood is called hyperglycemia. The body is unable to use the glucose for energy. This leads to the symptoms of type 1 diabetes.

    The Hypoglycemic States

    The Hypoglycemic States

    Spontaneous hypoglycemia in adults is of two principal types: fasting and postprandial. Symptoms begin ...

    Diabetes Complications

    Diabetes Complications

    The major cause of the high morbidity and mortality rate associated with...

    Chronic Complications of Diabetes

    Chronic Complications of Diabetes

    Late clinical manifestations of diabetes mellitus include a number of pathologic changes ...

    Diabetes Cardiovascular complications

    Diabetes Cardiovascular complications

    Cardiovascular disease risk is increased in patients with type 1 diabetes...

    Complications of Insulin Therapy

    Complications of Insulin Therapy

    Hypoglycemic reactions, the most common complication of insulin therapy...

    Diabetic Nephropathy

    Diabetic Nephropathy

    As many as 4000 cases of end-stage renal disease occur each year among diabetic people in the United States...

    Diabetic Neuropathy

    Diabetic Neuropathy

    Diabetic neuropathies are the most common complications of diabetes affecting...

    Diabetes Mellitus Management

    Primary treatment goals for diabetes patients include the achieving of blood glucose levels...

    Diabetes Mellitus and Oral Health

    About 16 million Americans have diabetes (between 6 and 7% of the total US population)...

    Essential update: Taiwanese study suggests enterovirus infection may be associated with increased risk of type 1 diabetes A nationwide, population-based cohort study in Taiwan has produced evidence linking enterovirus infection with the development of type 1 diabetes in children younger than age 18.

    Researchers looked at data from Taiwan's national health insurance system from 2000-2007 and found a total of 570,133 children had an enterovirus infection during that time. After matching with the same number of uninfected controls, data showed the overall incidence of type 1 diabetes was higher in adolescents who had been infected by enterovirus (5.73 versus 3.89 per 100,000), for an incidence rate ratio 1.48 of among infected children (95% CI 1.19-1.83).

    The exact cause of type 1 diabetes is unknown. Most likely it is an autoimmune disorder. This is a condition that occurs when the immune system mistakenly attacks and destroys healthy body tissue. With type 1 diabetes, an infection or another trigger causes the body to mistakenly attack the cells in the pancreas that make insulin. The tendency to develop autoimmune diseases, including type 1 diabetes, can be passed down through families.



    The following symptoms may be the first signs of type 1 diabetes. Or they may occur when blood sugar is high.

    • Being very thirsty
    • Feeling hungry
    • Feeling tired all the time
    • Having blurry eyesight
    • Feeling numbness or tingling in your feet
    • Losing weight without trying
    • Urinating more often (including urinating at night or bedwetting in children who were dry overnight before)
    • For other people, these serious warning symptoms may be the first signs of type 1 diabetes. Or, they may happen when blood sugar is very high (diabetic ketoacidosis):
    • Deep, rapid breathing
    • Dry skin and mouth
    • Flushed face
    • Fruity breath odor
    • Nausea or vomiting; inability to keep down fluids
    • Stomach pain


    Low blood sugar (hypoglycemia) can develop quickly in people with diabetes who are taking insulin. Symptoms usually appear when a person's blood sugar level falls below 70 milligrams per deciliter (mg/dL). Watch for:

    • Headache
    • Hunger
    • Nervousness
    • Rapid heartbeat (palpitations)
    • Shaking
    • Sweating
    • Weakness

    Exams and Tests

    Diabetes is diagnosed with the following blood tests:

    • Fasting blood glucose level: Diabetes is diagnosed if it is higher than 126 mg/dL two different times.
    • Random (non-fasting) blood glucose level. You may have diabetes if it is higher than 200 mg/dL, and you have symptoms such as increased thirst, urination, and fatigue. (This must be confirmed with a fasting test.)
    • Oral glucose tolerance test: Diabetes is diagnosed if the glucose level is higher than 200 mg/dL 2 hours after you drink a special sugar drink.
    • Hemoglobin A1c (A1C) test: Diabetes is diagnosed if the result of the test is 6.5% or higher.

    Ketone testing is also used sometimes. The ketone test is done using a urine sample or blood sample. Ketone testing may be done:

    • When the blood sugar is higher than 240 mg/dL
    • During an illness such as pneumonia, heart attack, or stroke
    • When nausea or vomiting occur
    • During pregnancy

    The following tests or exams will help you and your doctor monitor your diabetes and prevent problems caused by diabetes:

    • Check the skin and bones on your feet and legs.
    • Check if your feet are getting numb (diabetic nerve disease).
    • Have your blood pressure checked at least once a year. The goal should be 140/80 mm Hg or lower.
    • Have an A1C test done every 6 months if your diabetes is well controlled. Have the test done every 3 months if your diabetes is not well
    • controlled.
    • Have your cholesterol and triglyceride levels checked once a year.
    • Get tests once a year to make sure your kidneys are working well (microalbuminuria and serum creatinine).
    • Visit your eye doctor at least once a year, or more often if you have signs of diabetic eye disease.

    See the dentist every 6 months for a thorough dental cleaning and exam. Make sure your dentist and hygienist know that you have diabetes.


    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.


    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:

    • Excessive thirst
    • Feeling tired
    • Needing to urinate frequently
    • Losing weight
    • Blurred vision

    Less commonly, there are symptoms of a problem called diabetic ketoacidosis (DKA). People with DKA have symptoms of high blood sugar, 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.


    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.


    Several special situations can complicate insulin treatment. With advance planning and close monitoring, these situations are less likely to cause serious difficulties. A healthcare provider can help to handle these situations.

    Eating out - Eating out can be challenging since ingredients used, calorie and fat content, and portion sizes are usually different from meals prepared at home. You can estimate the carbohydrate content of meals to calculate insulin dose; nutrition information is often available from restaurants or a hand-held reference book.

    Low or high blood sugar levels can occur more easily in situations where new or different foods are eaten; a fast-acting source of carbohydrates (eg, candy, glucose tablets) and a blood glucose monitor should be kept on hand at all times.

    Surgery - Patients who have surgery may be instructed not to eat for 8 to 12 hours before their procedure. A healthcare provider can help to determine the dose and timing of insulin before and after the procedure, especially if you will be unable to eat a normal diet afterwards.

    Infections - Mild infections, such as a cold, sore throat, or urinary tract infection, can cause blood sugar levels to rise and can even lead to diabetic ketoacidosis. In this situation, frequent telephone contact with a healthcare provider, careful blood sugar monitoring, and increasing the insulin dose are often recommended. Patients with nausea or vomiting may require medication to control their symptoms and avoid dehydration and ketoacidosis. If dehydration occurs, treatment with intravenous (IV) fluids may be necessary.

    Travel - Managing blood sugar levels and insulin treatment while traveling can be difficult, especially when traveling across multiple time zones. In addition, activity levels and diet are often different while traveling, making careful blood sugar monitoring essential. Speak with your healthcare provider before traveling to develop a treatment plan.


    The pancreas produces very little or no insulin at all in people with type 1 diabetes. All patients with type 1 diabetes will eventually require insulin. Insulin must be given as a shot.

    Dosing - When you are first starting insulin, it will take some time to find the right dose. A doctor or nurse will help to adjust your dose over time. It is important to check your blood sugar level several times per day during this time.

    Insulin needs often change over your lifetime. Changes in weight, what you eat, health conditions (including pregnancy), activity level, and work can affect the amount of insulin needed to control your blood sugar.

    Many people are able to adjust their own insulin dose, although you will need help from time to time. Most people with type 1 diabetes meet with a doctor or nurse every three to four months; you will review your blood sugar levels and insulin doses at these visits, helping to fine-tune your diabetes control.

    Types - There are several different types of insulin. These types are classified according to how quickly they begin working and how long the insulin lasts:

    • Rapid-acting (eg, insulin lispro [Humalog], insulin aspart [Novolog], and insulin glulisine [Apidra])
    • Short-acting (eg, insulin regular)
    • Intermediate-acting (eg, insulin NPH)
    • Long-acting (eg, insulin glargine [Lantus], insulin detemir [Levemir])

    Insulin types can be used in combination to achieve around-the-clock blood sugar control.

    Type 1 diabetes mellitus and diet

    Diet and physical activity are critically important in the management of the ABCs (A1C, Blood pressure and Cholesterol) of type 1 diabetes. To effectively manage A1C (hemoglobin A1C) and achieve stable blood sugar control, it is important to understand how to balance food intake, physical activity, and insulin.

    Making healthy food choices every day has both immediate and long-term effects. With education, practice, and assistance from a dietitian and/or a diabetes educator, it is possible to eat well and control diabetes.


    Many factors affect how well diabetes is controlled. Many of these factors are controlled by the person with diabetes, including how much and what is eaten, how frequently the blood sugar is monitored, physical activity levels, and accuracy and consistency of medication dosing. Even small changes can affect blood sugar control.

    Eating a consistent amount of food every day and taking medications as directed can greatly improve blood sugar control and decrease the risk of diabetes-related complications, such as coronary artery disease, kidney disease, and nerve damage. In addition, these measures impact weight control. A dietitian can help to create a food plan that is tailored to your medical needs, lifestyle, and personal preferences.


    Consistently eating at the same times every day is important for some people, especially those who take long-acting insulin (eg, NPH). If a meal is skipped or delayed, you are at risk for developing low blood glucose.

    People who use intensive insulin therapy (those on an insulin pump or multiple daily insulin injections) have more flexibility around meal timing. With these regimens, skipping or delaying a meal does not usually increase the risk of low blood sugar.

    High fat meals - Foods or meals that are high in fat (eg, pizza) may be eaten occasionally, although blood glucose levels should be monitored more closely. High-fat meals are broken down more slowly than low-fat meals. When using rapid acting insulin (eg, Humalog, Novolog) before a meal, the blood sugar level may become low shortly after eating a high fat meal and then rise hours later.

    People who use an insulin pump can use an extended insulin delivery regimen to better manage blood sugar levels after eating a high-fat meal. People who give insulin injections do not generally adjust their treatment based upon the fat content of their meal.


    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.

    However, you can substantially lower your risk of cardiovascular disease by:

    • Not smoking
    • Taking a low-dose aspirin every day if indicated (for adults only)
    • Managing high blood pressure and high cholesterol with diet, exercise, and medications
    • Keeping your glycated hemoglobin (A1C) at 7 percent or lower


    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.