Type 2 diabetes is a condition that happens because of a problem in the way the body regulates and uses sugar as a fuel. That sugar also is called glucose. This long-term condition results in too much sugar circulating in the blood. Eventually, high blood sugar levels can lead to disorders of the circulatory, nervous and immune systems.
In type 2 diabetes, there are primarily two problems. The pancreas does not produce enough insulin — a hormone that regulates the movement of sugar into the cells. And cells respond poorly to insulin and take in less sugar.
Type 2 diabetes used to be known as adult-onset diabetes, but both type 1 and type 2 diabetes can begin during childhood and adulthood. Type 2 is more common in older adults. But the increase in the number of children with obesity has led to more cases of type 2 diabetes in younger people.
There's no cure for type 2 diabetes. Losing weight, eating well and exercising can help manage the disease. If diet and exercise aren't enough to control blood sugar, diabetes medications or insulin therapy may be recommended.
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Symptoms of type 2 diabetes often develop slowly. In fact, you can be living with type 2 diabetes for years and not know it. When symptoms are present, they may include:
- Increased thirst.
- Frequent urination.
- Increased hunger.
- Unintended weight loss.
- Blurred vision.
- Slow-healing sores.
- Frequent infections.
- Numbness or tingling in the hands or feet.
- Areas of darkened skin, usually in the armpits and neck.
When to see a doctor
See your health care provider if you notice any symptoms of type 2 diabetes.
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Type 2 diabetes is mainly the result of two problems:
- Cells in muscle, fat and the liver become resistant to insulin As a result, the cells don't take in enough sugar.
- The pancreas can't make enough insulin to keep blood sugar levels within a healthy range.
Exactly why this happens is not known. Being overweight and inactive are key contributing factors.
How insulin works
Insulin is a hormone that comes from the pancreas — a gland located behind and below the stomach. Insulin controls how the body uses sugar in the following ways:
- Sugar in the bloodstream triggers the pancreas to release insulin.
- Insulin circulates in the bloodstream, enabling sugar to enter the cells.
- The amount of sugar in the bloodstream drops.
- In response to this drop, the pancreas releases less insulin.
The role of glucose
Glucose — a sugar — is a main source of energy for the cells that make up muscles and other tissues. The use and regulation of glucose includes the following:
- Glucose comes from two major sources: food and the liver.
- Glucose is absorbed into the bloodstream, where it enters cells with the help of insulin.
- The liver stores and makes glucose.
- When glucose levels are low, the liver breaks down stored glycogen into glucose to keep the body's glucose level within a healthy range.
In type 2 diabetes, this process doesn't work well. Instead of moving into the cells, sugar builds up in the blood. As blood sugar levels rise, the pancreas releases more insulin. Eventually the cells in the pancreas that make insulin become damaged and can't make enough insulin to meet the body's needs.
Factors that may increase the risk of type 2 diabetes include:
- Weight. Being overweight or obese is a main risk.
- Fat distribution. Storing fat mainly in the abdomen — rather than the hips and thighs — indicates a greater risk. The risk of type 2 diabetes is higher in men with a waist circumference above 40 inches (101.6 centimeters) and in women with a waist measurement above 35 inches (88.9 centimeters).
- Inactivity. The less active a person is, the greater the risk. Physical activity helps control weight, uses up glucose as energy and makes cells more sensitive to insulin.
- Family history. An individual's risk of type 2 diabetes increases if a parent or sibling has type 2 diabetes.
- Race and ethnicity. Although it's unclear why, people of certain races and ethnicities — including Black, Hispanic, Native American and Asian people, and Pacific Islanders — are more likely to develop type 2 diabetes than white people are.
- Blood lipid levels. An increased risk is associated with low levels of high-density lipoprotein (HDL) cholesterol — the "good" cholesterol — and high levels of triglycerides.
- Age. The risk of type 2 diabetes increases with age, especially after age 35.
- Prediabetes. Prediabetes is a condition in which the blood sugar level is higher than normal, but not high enough to be classified as diabetes. Left untreated, prediabetes often progresses to type 2 diabetes.
- Pregnancy-related risks. The risk of developing type 2 diabetes is higher in people who had gestational diabetes when they were pregnant and in those who gave birth to a baby weighing more than 9 pounds (4 kilograms).
- Polycystic ovary syndrome. Having polycystic ovary syndrome — a condition characterized by irregular menstrual periods, excess hair growth and obesity — increases the risk of diabetes.
Type 2 diabetes affects many major organs, including the heart, blood vessels, nerves, eyes and kidneys. Also, factors that increase the risk of diabetes are risk factors for other serious diseases. Managing diabetes and controlling blood sugar can lower the risk for these complications and other medical conditions, including:
- Heart and blood vessel disease. Diabetes is associated with an increased risk of heart disease, stroke, high blood pressure and narrowing of blood vessels, a condition called atherosclerosis.
- Nerve damage in limbs. This condition is called neuropathy. High blood sugar over time can damage or destroy nerves. That may result in tingling, numbness, burning, pain or eventual loss of feeling that usually begins at the tips of the toes or fingers and gradually spreads upward.
- Other nerve damage. Damage to nerves of the heart can contribute to irregular heart rhythms. Nerve damage in the digestive system can cause problems with nausea, vomiting, diarrhea or constipation. Nerve damage also may cause erectile dysfunction.
- Kidney disease. Diabetes may lead to chronic kidney disease or end-stage kidney disease that can't be reversed. That may require dialysis or a kidney transplant.
- Eye damage. Diabetes increases the risk of serious eye diseases, such as cataracts and glaucoma, and may damage the blood vessels of the retina, potentially leading to blindness.
- Skin conditions. Diabetes may raise the risk of some skin problems, including bacterial and fungal infections.
- Slow healing. Left untreated, cuts and blisters can become serious infections, which may heal poorly. Severe damage might require toe, foot or leg amputation.
- Hearing impairment. Hearing problems are more common in people with diabetes.
- Sleep apnea. Obstructive sleep apnea is common in people living with type 2 diabetes. Obesity may be the main contributing factor to both conditions.
- Dementia. Type 2 diabetes seems to increase the risk of Alzheimer's disease and other disorders that cause dementia. Poor control of blood sugar is linked to a more rapid decline in memory and other thinking skills.
Healthy lifestyle choices can help prevent type 2 diabetes. If you've received a diagnosis of prediabetes, lifestyle changes may slow or stop the progression to diabetes.
A healthy lifestyle includes:
- Eating healthy foods. Choose foods lower in fat and calories and higher in fiber. Focus on fruits, vegetables and whole grains.
- Getting active. Aim for 150 or more minutes a week of moderate to vigorous aerobic activity, such as a brisk walk, bicycling, running or swimming.
- Losing weight. If you are overweight, losing a modest amount of weight and keeping it off may delay the progression from prediabetes to type 2 diabetes. If you have prediabetes, losing 7% to 10% of your body weight may reduce the risk of diabetes.
- Avoiding long stretches of inactivity. Sitting still for long periods of time can increase the risk of type 2 diabetes. Try to get up every 30 minutes and move around for at least a few minutes.
For people with prediabetes, metformin (Fortamet, Glumetza, others), a diabetes medication, may be prescribed to reduce the risk of type 2 diabetes. This is usually prescribed for older adults who are obese and unable to lower blood sugar levels with lifestyle changes.