Diabetes is a chronic (lifelong) disease marked by high levels of sugar in the blood.
Causes, incidence, and risk factors
Insulin is a hormone produced by the pancreas to control blood sugar. Diabetes can be caused by too little insulin, resistance to insulin, or both.
To understand diabetes, it is important to first understand the normal process by which food is broken down and used by the body for energy. Several things happen when food is digested:
- A sugar called glucose enters the bloodstream. Glucose is a source of fuel for the body.
- An organ called the pancreas makes insulin. The role of insulin is to move glucose from the bloodstream into muscle, fat, and liver cells, where it can be used as fuel.
People with diabetes have high blood sugar. This is because:
- Their pancreas does not make enough insulin
- Their muscle, fat, and liver cells do not respond to insulin normally
- Both of the above
There are three major types of diabetes:
- Type 1 diabetes is usually diagnosed in childhood. Many patients are diagnosed when they are older than age 20. In this disease, the body makes little or no insulin. Daily injections of insulin are needed. The exact cause is unknown. Genetics, viruses, and autoimmune problems may play a role.
- Type 2 diabetes is far more common than type 1. It makes up most of diabetes cases. It usually occurs in adulthood, but young people are increasingly being diagnosed with this disease. The pancreas does not make enough insulin to keep blood glucose levels normal, often because the body does not respond well to insulin. Many people with type 2 diabetes do not know they have it, although it is a serious condition. Type 2 diabetes is becoming more common due to increasing obesity and failure to exercise.
- Gestational diabetes is high blood glucose that develops at any time during pregnancy in a woman who does not have diabetes. Women who have gestational diabetes are at high risk of type 2 diabetes and cardiovascular disease later in life.
Diabetes affects more than 20 million Americans. Over 40 million Americans have pre-diabetes (early type 2 diabetes).
There are many risk factors for type 2 diabetes, including:
- Age over 45 years
- A parent, brother, or sister with diabetes
- Gestational diabetes or delivering a baby weighing more than 9 pounds
- Heart disease
- High blood cholesterol level
- Not getting enough exercise
- Polycystic ovary disease (in women)
- Previous impaired glucose tolerance
- Some ethnic groups (particularly African Americans, Native Americans, Asians, Pacific Islanders, and Hispanic Americans)
High blood levels of glucose can cause several problems, including:
- Blurry vision
- Excessive thirst
- Frequent urination
- Weight loss
However, because type 2 diabetes develops slowly, some people with high blood sugar experience no symptoms at all.
Symptoms of type 1 diabetes:
- Increased thirst
- Increased urination
- Weight loss in spite of increased appetite
Patients with type 1 diabetes usually develop symptoms over a short period of time. The condition is often diagnosed in an emergency setting.
Symptoms of type 2 diabetes:
- Blurred vision
- Increased appetite
- Increased thirst
- Increased urination
Signs and tests
A urine analysis may be used to look for glucose and ketones from the breakdown of fat. However, a urine test alone does not diagnose diabetes.
The following blood tests are used to diagnose diabetes:
- Fasting blood glucose level -- diabetes is diagnosed if higher than 126 mg/dL on two occasions. Levels between 100 and 126 mg/dL are referred to as impaired fasting glucose or prediabetes. These levels are considered to be risk factors for type 2 diabetes and its complications.
- Hemoglobin A1c test -- this test has been used in the past to help patients monitor how well they are controlling their blood glucose levels. In 2010, the American Diabetes Association recommended that the test be used as another option for diagnosing diabetes and identifying pre-diabetes. Levels indicate:
- Normal: Less than 5.7%
- Pre-diabetes: Between 5.7% - 6.4%
- Diabetes: 6.5% or higher
- Oral glucose tolerance test -- diabetes is diagnosed if glucose level is higher than 200 mg/dL after 2 hours. (This test is used more for type 2 diabetes.)
- Random (non-fasting) blood glucose level -- diabetes is suspected if higher than 200 mg/dL and accompanied by the classic diabetes symptoms of increased thirst, urination, and fatigue. (This test must be confirmed with a fasting blood glucose test.)
Persons with diabetes need to have their hemoglobin A1c (HbA1c) level checked every 3 - 6 months. The HbA1c is a measure of average blood glucose during the previous 2 - 3 months. It is a very helpful way to determine how well treatment is working.
Have your cholesterol and triglyceride levels checked each year (aim for LDL levels below 100 mg/dL).
The immediate goals are to treat diabetic ketoacidosis and high blood glucose levels. Because type 1 diabetes can start suddenly and have severe symptoms, people who are newly diagnosed may need to go to the hospital.
The long-term goals of treatment are to:
- Prolong life
- Reduce symptoms
- Prevent diabetes-related complications such as blindness, heart disease, kidney failure, and amputation of limbs
These goals are accomplished through:
- Blood pressure and cholesterol control
- Careful self testing of blood glucose levels
- Foot care
- Meal planning and weight control
- Medication or insulin use
There is no cure for diabetes. Treatment involves medicines, diet, and exercise to control blood sugar and prevent symptoms.
LEARN THESE SKILLS
Basic diabetes management skills will help prevent the need for emergency care. These skills include:
- How to recognize and treat low blood sugar (hypoglycemia) and high blood sugar (hyperglycemia)
- What to eat and when
- How to take insulin or oral medication
- How to test and record blood glucose
- How to test urine for ketones (type 1 diabetes only)
- How to adjust insulin or food intake when changing exercise and eating habits
- How to handle sick days
- Where to buy diabetes supplies and how to store them
After you learn the basics of diabetes care, learn how the disease can cause long-term health problems and the best ways to prevent these problems. Review and update your knowledge, because new research and improved ways to treat diabetes are constantly being developed.
If you have diabetes, your doctor may tell you to regularly check your blood sugar levels at home. There are a number of devices available, and they use only a drop of blood. Self-monitoring tells you how well diet, medication, and exercise are working together to control your diabetes. It can help your doctor prevent complications.
The American Diabetes Association recommends keeping blood sugar levels in a range based on your age. Discuss these goals with your doctor and diabetes educator.
- 70 - 130 mg/dL for adults
- 100 - 180 mg/dL for children under age 6
- 90 - 180 mg/dL for children 6 - 12 years old
- 90 - 130 mg/dL for children 13 - 19 years old
- Less than 180 mg/dL for adults
- 110 - 200 mg/dL for children under age 6
- 100 - 180 mg/dL for children 6 - 12 years old
- 90 - 150 mg/dL for children 13 - 19 years old
WHAT TO EAT
You should work closely with your health care provider to learn how much fat, protein, and carbohydrates you need in your diet. A registered dietician can help you plan your dietary needs.
People with type 1 diabetes should eat at about the same times each day and try to be consistent with the types of food they choose. This helps to prevent blood sugar from becoming extremely high or low.
People with type 2 diabetes should follow a well-balanced and low-fat diet.
See: Diabetes diet
HOW TO TAKE MEDICATION
Medications to treat diabetes include insulin and glucose-lowering pills called oral hypoglycemic drugs.
People with type 1 diabetes cannot make their own insulin. They need daily insulin injections. Insulin does not come in pill form. Injections are generally needed one to four times per day. Some people use an insulin pump. It is worn at all times and delivers a steady flow of insulin throughout the day. Other people may use inhaled insulin. See also: Type 1 diabetes
Unlike type 1 diabetes, type 2 diabetes may respond to treatment with exercise, diet, and medicines taken by mouth. There are several types of medicines used to lower blood glucose in type 2 diabetes. See also: Type 2 diabetes
Medications may be switched to insulin during pregnancy and while breastfeeding.
Gestational diabetes may be treated with exercise and changes in diet.
Regular exercise is especially important for people with diabetes. It helps with blood sugar control, weight loss, and high blood pressure. People with diabetes who exercise are less likely to experience a heart attack or stroke than those who do not exercise regularly.
Here are some exercise considerations:
- Always check with your doctor before starting a new exercise program.
- Ask your doctor or nurse if you have the right footwear.
- Choose an enjoyable physical activity that is appropriate for your current fitness level.
- Exercise every day, and at the same time of day, if possible.
- Monitor blood glucose levels before and after exercise.
- Carry food that contains a fast-acting carbohydrate in case you become hypoglycemic during or after exercise.
- Carry a diabetes identification card and a cell phone in case of emergency.
- Drink extra fluids that do not contain sugar before, during, and after exercise.
You may need to change your diet or medication dose if you change your exercise intensity or duration to keep blood sugar levels from going too high or low.
People with diabetes are more likely to have foot problems. Diabetes can damage blood vessels and nerves and decrease the body's ability to fight infection. You may not notice a foot injury until an infection develops. Death of skin and other tissue can occur.
If left untreated, the affected foot may need to be amputated. Diabetes is the most common condition leading to amputations.
To prevent injury to the feet, check and care for your feet every day.
For more information, see:
For additional information, see diabetes resources.
With good blood glucose and blood pressure control, many of the complications of diabetes can be prevented.
Studies have shown that strict control of blood sugar, cholesterol, and blood pressure levels in persons with diabetes helps reduce the risk of kidney disease, eye disease, nervous system disease, heart attack, and stroke.
Emergency complications include:
- Diabetic hyperglycemic hyperosmolar coma
- Diabetic ketoacidosis
Long-term complications include:
Calling your health care provider
Go to the emergency room or call the local emergency number (such as 911) if you have symptoms of ketoacidosis:
- Abdominal pain
- Deep and rapid breathing
- Increased thirst and urination
- Loss of consciousness
- Sweet-smelling breath
Go to the emergency room or call the local emergency number (such as 911) if you have symptoms of extremely low blood sugar (hypoglycemic coma or severe insulin reaction):
Maintaining an ideal body weight and an active lifestyle may prevent type 2 diabetes.
Currently there is no way to prevent type 1 diabetes.
There is no effective screening test for type 1 diabetes in people who don't have symptoms.
Screening for type 2 diabetes in people with no symptoms is recommended for:
- Overweight children who have other risk factors for diabetes starting at age 10 and repeating every 2 years
- Overweight adults (BMI greater than 25) who have other risk factors
- Adults over 45, repeated every 3 years
To prevent complications of diabetes, visit your health care provider or diabetes educator at least four times a year. Talk about any problems you are having.
Regularly have the following tests:
- Have your blood pressure checked every year (blood pressure goals should be 130/80 mm/Hg or lower).
- Have your glycosylated hemoglobin (HbA1c) checked every 6 months if your diabetes is well controlled, otherwise every 3 months.
- Have your cholesterol and triglyceride levels checked yearly (aim for LDL levels below 100 mg/dL, less than 70 mg/dL in high-risk patients).
- Get yearly tests to make sure your kidneys are working well (microalbuminuria and serum creatinine).
- Visit your ophthalmologist (preferably one who specializes in diabetic retinopathy) at least once a year, or more often if you have signs of diabetic retinopathy.
- See the dentist every 6 months for a thorough dental cleaning and exam. Make sure your dentist and hygienist know that you have diabetes.
- Make sure your health care provider inspects your feet at each visit.
Stay up-to-date with all of your vaccinations and get a flu shot every year in the fall.
Alemzadeh R, Wyatt DT. Diabetes Mellitus. In: Kliegman RM, ed. Kliegman: Nelson Textbook of Pediatrics. 18th ed. Philadelphia, Pa: Saunders;2007:chap 590.
American Diabetes Association. Diagnosis and classification of diabetes mellitus. Diabetes Care. 2010;33 Suppl 1:S62-S69.
American Diabetes Association. Standards of medical care in diabetes -- 2010. Diabetes Care. 2010; 33 Suppl 1:S11-S61.
Eisenbarth GS, Polonsky KS, Buse JB. Type 1 Diabetes Mellitus. In: Kronenberg HM, Melmed S, Polonsky KS, Larsen PR. Kronenberg: Williams Textbook of Endocrinology. 11th ed. Philadelphia, Pa: Saunders Elsevier; 2008:chap 31.
Reviewed By: Ari S. Eckman, MD, Division of Endocrinology and Metabolism, Johns Hopkins School of Medicine, Baltimore, MD. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.