Type 2 diabetes accounts for 95 percent of all diabetes cases. Type 2 diabetes occurs when your pancreas doesn’t make enough insulin due to problems with its beta cells, which produce the insulin, or when your body doesn’t use insulin properly, which is known as insulin resistance.

What is the main cause of type 2 diabetes?

Type 2 diabetes doesn’t have a single cause. In the majority of cases, it’s the result of a combination of genetic and lifestyle factors that work together to cause high blood sugar, which is the foundational characteristic of all types of diabetes.

Genetic factors for type 2 diabetes

Some genes may increase the likelihood that you’ll develop type 2 diabetes. Diabetes often—but not always—runs in families, and certain genetic mutations may explain why it occurs more often in certain racial and ethnic groups. 

While non-Hispanic whites account for 7.5 percent of diabetes cases:

  • Asian Americans account for 9.2 percent.
  • Non-Hispanic Blacks account for 11.7 percent. 
  • Hispanics account for 12.5 percent.
  • Alaska Natives and American Indians account for 14.7 percent.

Certain specific genes may increase or decrease your risk for type 2 diabetes. Researchers have identified at least 150 variations in DNA that directly or indirectly affect your risk, and it’s the combination of these genetic factors that determines, in part, whether you’re likely to develop diabetes. These genetic variations may predispose you to obesity, contribute to insulin resistance, or cause or contribute to other health conditions that increase your diabetes risk, including:

  • Cystic fibrosis, which causes scarring in the pancreas that can contribute to beta cell dysfunction
  • PCOS, a hormonal disorder common in pre-menopausal women that can lead to insulin resistance and diabetes
  • Hemochromatosis, a condition that causes the body to store too much iron, which can build up and damage the pancreas

What lifestyle factors contribute to type 2 diabetes?

Although you can’t control type 2 diabetes risk factors like your family history, genes, age, or ethnicity, there are a variety of lifestyle risk factors that you can control. Making lifestyle changes now can greatly reduce your risk of developing type 2 diabetes. If you’ve already been diagnosed with it, lifestyle changes can considerably lower your risk of developing the many complications associated with type 2 diabetes.

You’re more likely to develop type 2 diabetes if you are:

  • Overweight, which is defined as having a body mass index (BMI) of 25 or greater for people who are not Asian American or Pacific Islander; 23 or greater for Asian Americans; and 26 or greater for Pacific Islanders
  • Obese, which is defined as having a BMI of 30 or higher
  • Physically inactive, meaning you get less than 150 minutes of moderate exercise each week
  • A smoker

You’re also more likely to develop it if you have:

  • High blood pressure
  • Low “good” HDL cholesterol levels or high triglyceride levels
  • A history of stroke, heart disease, or gestational diabetes
  • Depression
  • Chronic stress
  • A poor diet

What lesser-known factors contribute to type 2 diabetes?

Other, less-common causes of type 2 diabetes may include damage to the pancreas by pancreatitis, pancreatic cancer, or trauma. Some medications may damage beta cells or interfere with how insulin works in the body. These include niacin, certain diuretics (water pills), some anti-seizure, psychiatric, HIV medications, and glucocorticoids, which are used to treat inflammatory conditions like rheumatoid arthritis, lupus, and asthma. 

Calculate your type 2 diabetes risk

Nearly one in five Americans has diabetes but doesn’t know it. The American Diabetes Association’s Diabetes Risk Test takes 60 seconds to complete and can give you important information about your likelihood of developing type 2 diabetes.

What are the symptoms of type 2 diabetes?

Early symptoms of diabetes are often subtle, and diabetes may not be the first thing that comes to mind if you experience them. While type 1 diabetes symptoms come on rather quickly, type 2 diabetes symptoms may appear gradually, over time—in some cases, people have had type 2 diabetes for years before they’re diagnosed. That’s why regular screening is so important. Following are the most common symptoms of type 2 diabetes.

Excessive thirst and increased frequency of urination

Diabetes is characterized by high blood glucose, which causes the kidneys to work extra hard to filter and absorb it. High blood sugar causes dehydration, and your body may pull fluid from organs and tissues in an effort to counteract the lack of fluids in your blood. If your kidneys can’t keep up with the absorption of the extra glucose, they’ll excrete it—and the extra fluids from your tissues—through your urine. This leaves you feeling very thirsty, and as you drink more fluids, you’ll urinate more frequently.


Fatigue is different from feeling sleepy or tired—it’s an overall lack of physical and mental energy, and it may cause weakness. The glucose in your blood is what fuels your body, and if the glucose isn’t making it into the cells in your muscles, brain, and other organs and tissues, you’ll feel less energetic. If you’re also dehydrated, the fatigue may be intensified.

Excessive hunger, even though you’re eating

When your cells can’t get enough energy from glucose, your muscles and organs send hunger messages to the brain, and you feel hungry more often than usual, even if you’re eating like you always have or you’re eating more than usual, due to the frequency of hunger.

Unexplained weight loss

Although unexplained weight loss is more commonly associated with type 1 diabetes, it may also occur with type 2 diabetes. That’s because when your body isn’t getting enough energy from the food you eat, it begins to break down your muscles and fat for energy, and you’ll lose weight—even if you’re eating normally.

Blurred vision

When your body attempts to get more fluids into your blood to counteract the high glucose levels, your eyes may be a source of those fluids. These fluid shifts can lead to blurry vision and trouble focusing.

Frequent infections or sores that heal slowly

High blood sugar can weaken your immune system function, leading to more infections or longer healing times for sores. In addition to weakening the immune system, high blood sugar promotes the growth of bacteria, leading to more frequent bacterial infections. The most common infections in people with type 2 diabetes include:

  • Fungal infections in the nose and throat, which may cause severe ear pain and ear discharge
  • Urinary tract infections, kidney infections, and inflammation in the bladder
  • Soft tissue and skin infections, especially in the legs and feet, which can take a long time to heal—and may lead to the need for amputation

Tingling in the hands or feet

Tingling, pain, burning, or numbness in the extremities—usually the feet and legs, but sometimes in the arms or hands—are early symptoms of diabetic neuropathy, a common but serious complication of diabetes. Your hands or feet may be sensitive to the touch, insensitive to hot or cold temperatures, or feel episodes of sharp pain or cramping. These may occur more often at night.

Swollen, red, or tender gums

Excessive levels of blood sugar can cause pain or infections in your mouth, including your teeth, gums, jaw, tongue, the insides of your cheeks, and the roof or bottom of your mouth. High glucose levels in your saliva promotes the growth of harmful bacteria, which can lead to gingivitis, or gum disease, or periodontitis, a severe form of gum disease.

When to get screened for diabetes

If you’re age 35 or older and you’re overweight or obese, you should get screened for diabetes every two years, even if you have no symptoms of diabetes. If you’re 35 or older, overweight or obese, and a member of one of the racial or ethnic groups that have higher occurrences of type 2 diabetes, your doctor may recommend more frequent screenings—especially if you have other risk factors, like a family history or an unhealthy lifestyle.

If you notice symptoms of diabetes, make an appointment with your physician right away for a diabetes screening. The sooner you’re diagnosed with type 2 diabetes, the sooner you can get your blood sugar under control through lifestyle changes or by taking medication for diabetes. Lifestyle changes and/or medication helps keep your blood sugar at healthy levels and can delay or even prevent diabetes complications.

Forward can help you prevent or manage type 2 diabetes

Diabetes is a major risk factor for heart disease, kidney disease, and many other serious health complications. With Forward as your primary care provider, you have access to resources that help you stay on top of preventive or management strategies for type 2 diabetes. Forward’s Heart Health Program, open to all members, includes genetic and blood testing, as well as a range of other assessments, to help identify your risk factors. A personalized preventive or management plan helps you address your specific risk factors, and ongoing monitoring and check-ins help you stay on track with your health goals. Our Weight Management Program can help you reach your weight loss goal to make managing your blood sugar easier. The Forward app gives you easy, instant access to your test results, health goals, and care team, and you can order your prescriptions, make appointments, or find current treatment and prevention guidance for a number of diseases and conditions. We make it easy to take control of your health and wellness so that you can live longer and enjoy a higher quality life.

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