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Type 2 Diabetes: Symptoms, Causes, Treatment

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People with diabetes often use a blood sugar monitoring device to help them test and control sugar levels. (Image credit: Dreamstime.)

Diabetes is a condition characterized by high blood sugar (glucose) levels, and Type 2 diabetes is the most common form.

Type 2 diabetes is a chronic disease, and left untreated, it can cause serious health complications. More than 29 million Americans have diabetes (the majority of which are Type 2), but 8 million don't know they have it, according to a 2014 report from the Centers for Disease Control and Prevention. And about 86 million U.S. adults have prediabetes, or blood sugar levels that are abnormally high, but not high enough to be classified as diabetes.


A hormone called insulin helps sugar get inside cells, which can then be used for energy. When the body's cells fail to respond properly to insulin, sugar builds up in the bloodstream, eventually leading to Type 2 diabetes.

Exactly why the body fails to respond to insulin, a phenomenon called insulin resistance, is not known, but risk factors include being overweight, inactive or older than 45. It is thought that increases in body fat makes it harder for the body to use insulin.

In contrast to Type 2 diabetes, Type 1 diabetes occurs when the pancreas makes little or no insulin.


According to the National Institutes of Health, early symptoms of Type 2 diabetes include increased thirst, increased urination, hunger, fatigue and more frequent or slow to heal infections, such as bladder, kidney and skin infections. Some people with the condition do not experience symptoms for many years.

Unexplained weight loss can also be a symptom of Type 2 diabetes, said Dr. Minisha Sood, an endocrinologist at Lenox Hill Hospital in New York City. This symptom can sometimes be confusing to patients, because diabetes is associated with obesity and too much weight gain, Sood said. Although this is true, Type 2 diabetes can lead to weight loss, mostly through a decrease in "water weight," Sood said.

"When blood sugar exceeds a certain level…the body has to eliminate that sugar somehow," Sood said. This is mostly done through the kidneys, and the body also gets rid of water along with the sugar, Sood said. "Patients end up losing a lot of water," she said.

After many years, Type 2 diabetes can lead to serious health issues, including eye problems and blindness, nerve damage that causes pain, tingling and numbness, kidney damage and poor blood flow to the legs and feet, the NIH says.

"Glucose can be toxic to blood vessels," Sood said, and damage to blood vessels over time is what causes some of these serious symptoms.


Some people learn they have diabetes through routine blood testing, such as when a doctor checks blood glucose levels during an annual exam, or for diabetes screening, Sood said. (Diabetes screening is recommended for overweight children starting at age 10, overweight adults who have other risk factors, and adults over age 45, according to the NIH).

Normal blood sugar varies from person to person, but a normal range for fasting blood sugar (the amount of glucose in your blood six to eight hours after a meal) is between 70 and 100 milligrams per deciliter. For most individuals, the level of glucose in the blood rises after meals. A normal blood-sugar range after eating is between 135 and 140 milligrams per deciliter.

According to the NIH, people are diagnosed with diabetes if:

  • They have a fasting blood glucose level of 126 mg/dL or higher, on two separate tests
  • They have a blood glucose level of higher than 200 mg/dL two hours after they drink a special sugar solution. (This is known as an oral glucose tolerance test).
  • They have a hemoglobin A1c test result of 6.5 percent or higher

People who have a family history of Type 2 diabetes should talk to their doctor about being screened for the condition, Sood said, because a family history of the disease increases the risk of developing Type 2 diabetes.

"If it's screened for an identified early, changes can be implement that could prevent progression of the disease, and complications," Sood told Live Science. 


The initial focus of diabetes treatment is to lower blood sugar levels. People with Type 2 diabetes should consult with their doctor about how often they should check their blood sugar levels, which is done with a device called a glucose meter, according to the NIH. Keeping track of your glucose levels will let you and your doctor know if changes need to be made to your diet, activity or medications.

It is important for people with Type 2 diabetes to manage their weight and have a well-balanced diet. While there is no one "diabetes diet," patients should focus on eating more fruits, vegetables and whole grains, and less refined carbohydrates and sweets, according to the Mayo Clinic.

Physical activity is also important, and those with Type 2 diabetes should aim to exercise for at least 30 minutes at day. While some people can control Type 2 diabetes with diet and exercise alone, others may need to take medications, such as metformin, according to Mayo. Some people with Type 2 diabetes may need insulin injections.

Weight loss surgery, or bariatric surgery, is also an option for very obese patients who have trouble managing their diabetes with diet, exercise and medications, the NIH says.

Sood said she recommends people who are diagnosed with Type 2 diabetes lose at least five to 10 percent of their current body weight. If it is clear that lifestyle changes will not be enough to get a person's blood sugar levels under control "then we start medications right away," Sood said. But lifestyle changes are always encouraged on top of medication use, she said.


Type 2 diabetes has traditionally been seen as a progressive disease that is managed rather than cured. Just because a patient can stop taking diabetes medications does not mean their diabetes is cured, the NIH says.

But recent studies have suggested that in some cases, Type 2 diabetes can be reversed with weight loss surgery, or by following an extreme diet that mimics surgery. A 2011 study in the journal Science Translational Medicine said that about 50 to 80 percent of patients who have gastric bypass surgery (a type of weight-loss surgery) see a reduction in their blood glucose levels that's enough for them to be considered free of Type 2 diabetes.

Another study, published in 2011 in the journal Diabetologia, found that people with Type 2 diabetes who followed an extreme diet of extreme diet of just 600 calories a day saw their blood glucose levels return to normal in about a week, and most were still diabetes-free three months after they stopped the diet. However, the study was small, with just 11 people, and experts say that such an extreme diet would be hard to keep up, and it's not clear how long diabetes will remain in remission after the diet is stopped.

A 2012 study from the Centers for Disease Control and Prevention found that some people may be able to return their blood sugar levels to normal by following a diet and exercise program, although this is very rare. In the study, which involved 4,500 people with Type 2 diabetes, 1.3 percent were able to achieve normal blood sugar levels with diet and exercise.

This article is for informational purposes only, and is not meant to offer medical advice.

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Rachael Rettner

Rachael has been with Live Science since 2010. She has a master's degree in journalism from New York University's Science, Health and Environmental Reporting Program. She also holds a B.S. in molecular biology and an M.S. in biology from the University of California, San Diego. Her work has appeared in Scienceline, The Washington Post and Scientific American.