Type 2 diabetes is a condition in which the body resists the insulin that is produced by the pancreas and may fail to make enough insulin to maintain normal glucose (blood sugar) levels. It is by far the most common form of diabetes.

About 19 million Americans, many of them undiagnosed, have type 2 diabetes, according to the National Institutes of Health. The incidence of type 2 diabetes has soared in the United States and worldwide in recent years, largely because of growing rates of obesity.

The exact cause of type 2 diabetes is unknown. However, it is associated with certain factors, including obesity, lack of exercise, age, a family history of diabetes, ethnicity and a history of gestational diabetes. Those at risk of developing this form of diabetes can prevent or delay the onset of the disease by achieving a healthy weight, eating a healthy diet and exercising more.

The symptoms of type 2 diabetes develop slowly. They may include fatigue, blurry vision and increases in hunger, thirst, urination and infections. Sometimes people have only mild symptoms or none at all. It is not uncommon for a person to have type 2 diabetes for years before being diagnosed through a glucose test.

Diabetes increases a person’s risk of developing serious complications, including nerve, eye, kidney and blood vessel disease. Treatment, including a combination of diet and exercise and sometimes insulin or antidiabetic agents, can control glucose levels and prevent or delay the onset of many of these complications.

Type 2 diabetes is a disease of metabolism. Under normal circumstances, the food people eat is converted into glucose (blood sugar) during digestion. Glucose is carried in the bloodstream and moved into the cells through the action of a hormone called insulin. Insulin acts as a key to open the cells to glucose. Without insulin the body cannot access the glucose. Cells require the glucose for energy.

In type 1 diabetes, an autoimmune disease in which the body mistakenly attacks the pancreas, people produce little or no insulin. In type 2 diabetes, the body either produces insufficient amounts or has trouble using insulin. In either case, the glucose builds up in the bloodstream until it is excreted in the urine.

Type 2 diabetes is by far the most common form of diabetes. The U.S. National Institutes of Health (NIH) estimated in 2006 that 20.8 million Americans – 7 percent of the population – had diabetes in 2005, 6.2 million of them undiagnosed. Of the diabetic population, an estimated 90 to 95 percent (18.7 million to 19.8 million people) had type 2 diabetes.

Only 5.8 million Americans were diagnosed with diabetes in 1980, and the total in 1996 was still below 9 million, according to the U.S. Centers for Disease Control and Prevention (CDC). The soaring incidence of type 2 diabetes in recent years is blamed largely on the soaring incidence of obesity, due to physical inactivity and overeating.

There are several reasons why people develop type 2 diabetes:

• Muscle and fat cells become resistant to insulin. Obesity contributes to this insulin resistance.
  
  
• Pancreatic beta cells do not release enough insulin to meet the body’s needs.
  
  
• The liver releases too much glucose into the bloodstream.

Type 2 diabetes usually appears in middle-aged and older adults but is increasingly being diagnosed in children and adolescents. Once diagnosed, patients will have to take action to prevent the following glucose problems associated with type 2 diabetes:

• Hyperglycemia. Abnormally high glucose. Left untreated, it can lead to coma or death.
  
  
• Hypoglycemia. Abnormally low glucose. Left untreated, it can lead to convulsions, unconsciousness or brain damage.
  
  
• Hyperosmolar hyperglycemic nonketotic syndrome (HHNS). A dangerous condition involving severe hyperglycemia and dehydration. Left untreated, HHNS can lead to seizures, coma or death.

Type 2 diabetes significantly increases a person’s risk of developing many serious complications, including:

• Heart conditions and stroke. Cardiovascular disease is the No. 1 killer of people with type 2 diabetes.

• Eye diseases (diabetic retinopathy, glaucoma, cataracts, macular degeneration) and blindness.
  

• The kidney disease diabetic nephropathy and chronic kidney failure.
  
  
• The nerve disease diabetic neuropathy, including gastroparesis.
  
  
• Foot problems and leg amputations.
  
  
• Skin disorders.
  
  
• Decreased cognitive abilities and dementia.
  
  
• Sexual dysfunction.
  
  
• Pregnancy complications.
  
  
• Some types of cancer.
  
  
• Urinary incontinence.
  
  
• Yeast infections, urinary tract infections, gingivitis, thrush, tuberculosis and other infections.

In addition, recent research has found an increased prevalence of asthma and Parkinson’s disease in people with type 2 diabetes.

Type 2 diabetes was once known as noninsulin-dependent diabetes mellitus (NIDDM) or adult-onset diabetes. However, those terms are not accurate because some people with type 2 diabetes need to take insulin, and increasing numbers of children are being diagnosed with the disease. Federal health statistics revealed in 2005 that about 2 million U.S. adolescents have prediabetes, a condition that often leads to type 2 diabetes.

Diabetes is the sixth-leading cause of death in the United States and contributes to hundreds of thousands of other deaths a year but is often underreported in mortality statistics, according to the NIH. The overall U.S. death rate fell 32 percent from 1970 to 2002, but the death rate from diabetes rose 45 percent, according to an analysis by the American Cancer Society in 2005.

Type 2 diabetes is growing throughout the world, especially where prosperity and the adoption of Western lifestyles are increasing, such as India and China. The International Diabetes Federation estimates that 230 million people have diabetes and projects this figure to reach 350 million by 2025. It warns that, if trends continue, type 2 diabetes may within 25 years become the largest epidemic the world has ever experienced. Using revised methodology, the World Health Organization estimated in 2005 that 2.9 million people globally died of diabetes in 2000, about three times its previous estimate.

Recent large-scale studies found that two-thirds of Americans and half of Canadians with type 2 diabetes had poor control of their glucose. However, the CDC reported in 2005 that U.S. hospitalizations for diabetic complications decreased 35 percent from 1994 to 2002. 

A number of factors have been shown to increase the risk of developing type 2 diabetes. They include:

• Weight. Being overweight or obese is the leading risk factor for type 2 diabetes. Although it can occur in lean people (especially the elderly or people with a family history of the disease), about 80 percent of cases occur in people who are overweight. The more fatty tissue a person has, the more resistant the cells become to the individual’s own insulin.
  
  A healthy weight range can be determined by methods including a person’s body mass index (BMI). A person with a BMI of 25 to 29.9 is considered overweight. A person with a BMI of 30 or more is considered obese.
  
  The distribution of the weight is also a factor. People with excess weight above their hips, especially around their abdomen, are at a higher risk than those with excess weight on their hips and thighs.
  
  
• Activity level. The less physically active a person is, the greater the risk for type 2 diabetes because inactivity contributes to obesity, high blood pressure and unhealthy cholesterol levels. In addition, the body uses glucose for energy during exercise and helps to lower insulin resistance.
  
  
• Age. A person’s risk of developing type 2 diabetes increases with age. The disease is especially prevalent in those age 45 and over because people tend to exercise less, lose muscle mass and gain weight as they age. According to the American Diabetes Association (ADA), 20 percent of people over the age of 65 have type 2 diabetes.
  
  Although type 2 diabetes usually appears in middle-aged and older adults, it is increasingly being diagnosed in children and adolescents. The increase is most likely due to the rise in obesity, physical inactivity and poor eating habits in this population. When type 2 diabetes develops in children, it most often occurs during mid-puberty, a time when hormone levels are changing. These changes cause insulin resistance and decreased insulin secretion.
  
  
• Race/ethnicity and genetics. Type 2 diabetes is more common in African Americans, Hispanics/Latinos, Native Americans, Alaska Natives, Asian Americans and Pacific Islanders.
  
  Some researchers believe that these groups have inherited a “thrifty” gene that helped their ancestors survive during cycles of feast and famine. The gene enabled people to store energy in the body more efficiently during times when food was plentiful, in order to survive during times when food was scarce. This gene may be responsible for putting these groups at a higher risk of developing type 2 diabetes.
  
  The increased risk has also been attributed to changes in dietary practices, poverty, lack of access to health care, an increase in obesity and decrease in physical activity within these groups.
  
  Although type 2 diabetes is more common in some groups, the ADA does not consider race or ethnicity alone a statistically significant predictor of diabetes. Age, weight and activity level are more important factors.
  
  
• Family history. People’s risk of developing type 2 diabetes increases if their mother, father, sister or brother has the disease. The increase is most likely linked to the inheritance of certain genes.
  
  
• Sex. Though men make up less than half the U.S. adult population, they account for 53 percent of the adult cases of diabetes, according to the National Institutes of Health (NIH). The prevalence of diabetes in men and women was similar until 1999, when a growing disparity began, according to the U.S. Centers for Disease Control and Prevention (CDC). Little or no research has been conducted to account for the discrepancy.
  
  
• Prediabetes. People almost always have prediabetes before they develop type 2 diabetes.
  
  
• High blood pressure (hypertension). People with elevated blood pressure are at a greater risk of developing type 2 diabetes than those with normal blood pressure. Blood pressure above 140/90 millimeters of mercury (mm Hg) is considered high. 

• Unhealthy cholesterol levels. Patients with unhealthy cholesterol levels are at a greater risk of developing type 2 diabetes, and conversely those with type 2 diabetes are often found to have abnormally high lipid levels. High levels of triglycerides and low-density lipoprotein (LDL) cholesterol and low levels of high-density lipoprotein (HDL) cholesterol are considered unhealthy.
  
  
• Metabolic syndrome. This cluster of conditions can include prediabetes, abdominal obesity, high blood pressure and unhealthy levels of blood lipids.
  
  
• History of gestational diabetes. Women who develop this temporary form of diabetes during pregnancy are at a greater risk of developing type 2 diabetes later in life, particularly if they gain weight. The link may be related to the insulin resistance associated with both conditions.
  
  
• Giving birth to a baby weighing more than 9 pounds (macrosomia). Delivering at least one baby weighing more than 9 pounds is associated with an increased chance of the mother developing type 2 diabetes later in life. The oversized infant may also be increased risk.
  
  
• Low birth weight. Studies have shown that babies born weighing less than 5.5 pounds have a more difficult time processing glucose in their bodies than babies born at a normal weight. This may put people at an increased risk of type 2 diabetes later in life.
  
  
• • Acanthosis nigricans. This skin condition may appear in overweight people who are insulin resistant.
    
    
  • Polycystic ovarian syndrome (PCOS). This hormonal imbalance in females is linked to insulin resistance and type 2 diabetes.
    
    
• Smoking. People who smoke cigarettes are at a higher risk of developing type 2 diabetes than people who do not smoke.
  
  
• Exposure to Agent Orange. People who were exposed to the herbicide Agent Orange are at a greater risk for developing type 2 diabetes because there is an apparent connection between exposure and insulin resistance. In 2005, the U.S. Department of Defense finished analysis of its 20-year Air Force Health Study by concluding that type 2 diabetes was the most important health problem found in the crewmen who sprayed Agent Orange during the Vietnam War.
  
  
• Certain medications. Certain medications. Drugs that have linked to increased risk of diabetes include corticosteroids, some antihypertensives (beta blockers and diuretics), antidepressants, antipsychotics, antiretrovirals (HIV drugs), chemotherapy drugs and estrogens.
  
  
• Certain diseases. Some studies have linked conditions including fatty liver disease, gout, hemochromatosis, hepatitis C, pancreatitis and certain chromosomal and genetic disorders to increased risk of type 2 diabetes.

• Sleep irregularities. Some studies have linked insufficient sleep or excess sleep to increased risk of type 2 diabetes.

Over time, drinking large amounts of alcohol may increase a person’s risk of developing type 2 diabetes. However, some studies have shown that drinking a moderate amount of alcohol may reduce the odds of developing type 2 diabetes and other conditions such as heart disease. Patients are advised to ask their physician about the risks and benefits of moderate consumption of alcohol.

Diabetes often goes undiagnosed because many of its symptoms do not seem very unusual. Though symptoms of type 1 diabetes typically develop over a short period of time, symptoms of type 2 diabetes develop at a slower pace. Sometimes people have only mild symptoms or do not experience symptoms at all.

It is not uncommon for a person to have type 2 diabetes for years before being diagnosed. For this reason, it is important for people at risk to be aware of the symptoms. Common symptoms include:

• Frequent urination (polyuria) and dehydration
• Excessive thirst (polydipsia)
• Extreme hunger (polyphagia)
• Unexplained weight loss
• Increased fatigue
• Numbness or tingling in hands or feet
• Dry, itchy skin
• Slow-healing sores
• Red, swollen or tender gums or gingivitis

• Frequent infections, including urinary tract infections and yeast infections
• Blurry vision
• Dizziness
• Irritability

Symptoms vary from person to person. People experiencing any of these symptoms are encouraged to see a physician.

Though symptoms can point to diabetes, the only way for a physician to diagnose diabetes is with blood tests. When physicians determine that a blood test result is outside of normal range, they may order repeat tests to verify results or additional tests to determine the underlying causes behind the abnormality. Common tests for diagnosing diabetes include:

• Random plasma glucose test. This test may be conducted as a part of a routine physical examination. Glucose levels above 200 milligrams per deciliter (mg/dL) accompanied by symptoms will lead to a diabetes diagnosis. A fasting glucose test may be obtained to confirm the results. 
  
  
• Fasting blood glucose test (FPG). Normal fasting blood glucose is below 100 mg/dL. Glucose levels of 126 mg/dL or above will lead to a repeat test. If the results of the second test are the same, the patient will most likely be diagnosed with diabetes.
  
  
• Oral glucose tolerance test (OGTT). Normal blood sugar is below 140 mg/dL two hours after consuming a glucose-rich drink. If the level rises to 200 mg/dL or above, the person will most likely be diagnosed with diabetes.

The American Diabetes Association (ADA) recommends that anyone age 45 or older have a FPG, especially if overweight or obese. If results are normal, the patient should be retested again every three years. Patients diagnosed with prediabetes should be checked for type 2 diabetes every one to two years.

For overweight adults younger than 45, a physician may recommend testing if any other risk factor for diabetes is present. 

Children and adolescents who are at risk should be screened for diabetes every two years after the age of 10, or at the onset of puberty if it occurs at an earlier age.

Once diagnosed, the immediate goal for patients is to stabilize their glucose (blood sugar) levels. Their physician will recommend a target glucose range. The patient will aim to keep glucose levels within the physician-recommended range with a combination of diet and exercise, usually along with antidiabetic agents and sometimes insulin.

Usually, the first treatment for type 2 diabetes is meal planning, weight loss and exercise. Nutrition counseling and meal planning often involve cutting calories, replacing a few large meals a day with several small meals, replacing sugars and starches with nutritious high-fiber complex carbohydrates, and trading saturated fats and trans fats for lean protein and monounsaturated and polyunsaturated fats.

Losing weight and increasing activity levels can help lower the body’s resistance to insulin. Exercise also reduces glucose levels by taking glucose from the blood and using it for energy. For those with various medical conditions outlined below, exercise programs need to be carefully monitored by a physician.

When these steps are not enough to bring glucose levels down near the normal range, the physician may recommend medication.

Type 2 diabetes may be treated with glucose-lowering medications, and if these agents fail to control blood sugar, the physician may prescribe insulin.

Antidiabetic agents used to treat type 2 diabetes include:

• Alpha-glucosidase inhibitors. Block the breakdown of complex carbohydrates in the intestine, as well as some simple carbohydrates.
  
  
• Biguanides. Decrease the amount of glucose produced by the liver. They may also lower insulin resistance in the muscles.
  
  
• Meglitinides. Stimulate the beta cells of the pancreas to release more insulin in response to a meal.
  
  
• Sulfonylureas. Stimulate the beta cells to produce and release more insulin.
  
  
• Thiazolidinediones. Lower insulin resistance. This helps insulin work better in muscles and fat cells and reduces glucose production in the liver.
  
  
• DPP-4 inhibitors. Affect the pancreatic alpha cells and beta cells to reduce release of glucose from the liver and increase production of insulin.
  
  
• Incretin mimetics. Injected medications that promote insulin production by the beta cells and perhaps restore the beta cells themselves. They may also make the body more sensitive to insulin and promote weight loss.
  
  
• Synthetic amylin. Injected drug that may be prescribed to people who have unstable diabetes despite the use of insulin.
  
  
• Combination antidiabetic agents. A combination of medications can be used to treat type 2 diabetes.

The physician may also prescribe other medications including diet pills to reduce obesity, antihypertensives to lower blood pressure and cholesterol drugs to improve levels of blood fats.

A physician may also recommend insulin therapy. According to the American Diabetes Association, 30 to 40 percent of patients diagnosed with type 2 diabetes use insulin therapy to control their diabetes. Patients may need to take insulin on its own or in addition to antidiabetic agents. Forms of insulin administration include syringe injections, insulin pens, insulin pumps, jet injectors and inhaled insulin.

Daily glucose testing may be necessary. Glucose monitoring can alert patients when their glucose levels are above or below their target range. If readings are frequently out of range, a physician may recommend a change in the patient’s diabetes management plan.

Type 2 diabetes increases a person’s risk of developing many serious complications such as nerve, eye, kidney and blood vessel damage. Patients can delay or prevent the onset of these complications by controlling their glucose, cholesterol and blood pressure. However, many diabetic individuals do not meet their recommended goals.

Patients will require regular medical checkups to screen for developing problems. According to recommendations of national healthcare organizations, at each visit with their healthcare provider, patients should have the following checked:

• Blood pressure
• Weight
• Feet
• Eyes

At least twice a year, patients should have:

• Glycohemoglobin tests
• Dental exams and teeth cleanings (every three months for many patients)
• Visit with their endocrinologist

Once a year, the ADA recommends that diabetic individuals have:

• A cholesterol test. (Some people may need to be tested more often.)
  
  
• A dilated eye exam by an ophthalmologist.
  
  
• A complete foot exam, including inspection and sensation checks. (Patients with neuropathy or deformities such as hammertoes or bunions may need to have more frequent foot exams.)
  
  
• Urine tests for proteinuria
  
  
• A flu shot

In addition to these guidelines, patients with type 2 diabetes should also have a pneumonia vaccination at least once in their lifetime. Patients who are 65 and those suffering from chronic illness or a weakened immune system may require an additional pneumonia shot five to 10 years after their first one.

A physician can create a sick-day plan in advance to help patients cope with infections and other health problems.

Patients may need to see various specialists to screen for or treat complications ranging from heart conditions to sexual dysfunction. Recent research suggests suggests that screening procedures such as a stress test can find coronary artery disease in many people with type 2 diabetes, even those with no cardiac symptoms or risk factors. Patients may wish to ask their physician if such screening methods are recommended for them.

Studies including the landmark Diabetes Prevention Program have shown that lifestyle changes can prevent or delay the onset of type 2 diabetes in people with a high risk. Some of the most common strategies include:

• Eating a good diet. Dietitians typically recommend a balanced diet low in sugar, high in fiber, low in saturated fats, and adequate in monounsaturated fats, omega-3 fats and protein.
  
  
• Losing weight and maintaining a healthy weight. Fat makes cells more resistant to insulin. Most cases of type 2 diabetes occur in people who are overweight or obese. Losing weight can make cells more receptive to insulin and restore glucose (blood sugar) levels to a normal range. Even a modest weight loss of 10 to 15 pounds can be enough to make a difference. People at a healthy weight should maintain it.
  
  
• Exercising. Engaging in regular exercise lowers glucose levels and helps the body to use insulin. Even moderate exercise, such as walking for 30 minutes five days a week, can also contribute to weight loss, keep blood pressure down and reduce cholesterol levels. Patients should consult with their physician before starting an exercise program. This is particularly important if someone has a history of heart disease, high blood pressure, vascular disease such as atherosclerosis, or disorders of the feet or legs.
  
  
• Controlling cholesterol. A person’s total cholesterol level (which includes LDL, HDL and triglycerides) should be no more than 200 milligrams per deciliter (mg/dL) and no more than five times the HDL level. Regular exercise and a heart-healthy diet can reduce levels of total cholesterol, LDL cholesterol and triglycerides. If these strategies are unsuccessful, a physician may prescribe cholesterol-reducing drugs. Researchers reported in 2005 that one fibrate, a type of cholesterol drug, may postpone the onset of type 2 diabetes in obese people.

• Controlling high blood pressure (hypertension). The target blood pressure for most people is below 120/80 millimeters of mercury (mm Hg). Hypertension can be controlled through self-monitoring, eating a heart-healthy, low-salt diet, engaging in regular exercise and taking blood pressure medications if necessary.  ACE inhibitors and angiotensin-II receptor blockers (ARBs) might lower the risk of developing type 2 diabetes.
  
  
• Watching intake of alcohol. Alcohol affects the clearance of fat from the liver, increases high blood pressure and raises levels of triglycerides in the blood. It is also high in calories and may contribute to weight gain. Some studies have found that modest consumption of alcohol may reduce risk of diabetes and cardiovascular disease, but heavy consumption is a risk factor for diabetes and many other health problems.
  
  
• Quitting smoking (or not starting to smoke). In addition to causing lung disease, smoking raises blood pressure and raises blood glucose levels.
  
  
• Breastfeeding. Two major studies involving more than 157,000 women found that the longer women breastfed, the more they lowered their risk of developing type 2 diabetes.

Scientists are conducting a great deal of research into type 2 diabetes. Much of the emphasis is on development of additional antidiabetic agents and medications that can treat risk factors such as obesity, cholesterol and high blood pressure and complications such as diabetic retinopathy, diabetic nephropathy and diabetic neuropathy.

The genetics of type 2 diabetes is another focus. In 2005, researchers in Iceland announced discovery of a gene variant called TCF7L2 that could predispose close to 38 percent of Northern European populations and many black Americans to type 2 diabetes. Researchers in Boston used new DNA technology to implicate an ARNT gene (aryl hydrocarbon receptor nuclear translocator) in the development of type 2 diabetes. Further research on such findings could lead to treatments.

Researchers at the University of California, Los Angeles (UCLA) announced in early 2006 that a small-scale study suggested that a three-week high-fiber, low-fat diet combined with daily exercise could reverse type 2 diabetes or metabolic syndrome. However, scientists and physicians generally consider diabetes a lifelong condition that can be managed rather than cured. Rigorous follow-up would be required before this view is changed.

Preparing questions in advance can help patients have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions about type 2 diabetes:

1. Do I have or am I at risk of developing type 2 diabetes?
   
   
2. If I have prediabetes or diabetic risk factors, how can I prevent type 2 diabetes?
   
   
3. What diagnostic tests do I need to undergo?
   
   
4. What do my test results show?
   
   
5. What are my treatment options? Do I need to take pills, insulin or other medication?
   
   
6. Do I need to lose weight?
   
   
7. What exercise plan should I follow?
   
   
8. What diet should I follow? Do you recommend I see a dietician?
   
   
9. How often should I be monitored by a physician?
   
   
10. What specialists do I need to see, and how often?
    
    
11. How often should I monitor my glucose? What’s the best way?
    
    
12. What is the best glucose range for me?
    
    
13. How can I avoid diabetic complications such as eye disease, kidney disease and heart disease?
    
    
14. Are others in my family at higher risk of diabetes? Should they be tested?
    
    
15. If my child has type 2 diabetes, what do I need to know?