Type 2 Diabetes Causes and Risk Factors

Medically Reviewed by Poonam Sachdev on June 22, 2023
4 min read

Not everyone with type 2 diabetes is overweight, but obesity and an inactive lifestyle are two of the most common causes of type 2 diabetes. These things are responsible for about 90% to 95% of diabetes cases in the United States.

When you're healthy, your pancreas (an organ behind your stomach) releases insulin to help your body store and use sugar from the food you eat. Diabetes happens when one or more of the following happens:

  • Your pancreas doesn't make any insulin.
  • Your pancreas makes very little insulin.
  • Your body doesn’t respond the way it should to insulin.

Unlike people with type 1 diabetes, people with type 2 diabetes make insulin. But the insulin their pancreas releases isn’t enough, or their body can't recognize the insulin and use it properly. (Doctors call this insulin resistance.)

When there isn't enough insulin or the insulin isn't used as it should be, glucose (a type of sugar) can't get into your cells. It builds up in your bloodstream instead. This can damage many areas of the body. Also, since cells aren't getting the glucose they need, they don't work the way they should.

Type 2 diabetes is believed to have a strong genetic link, meaning that it tends to run in families. If you have a parent, brother, or sister who has it, your chances rise. Several genes may be related to type 2 diabetes. 

Ask your doctor about a diabetes test if you have any of the following risk factors:

  • High blood pressure
  • High triglyceride levels. It's too high if it's over 500 milligrams per deciliter (mg/dL).
  • Low HDL cholesterol level. It's too low if it's less than 40 mg/dL for men, or 50 mg/dL for women.
  • Gestational diabetes or giving birth to a baby weighing more than 9 pounds
  • Prediabetes. That means your blood sugar level is above normal, but you don't have the disease yet.
  • Heart disease
  • A diet high in fat and carbohydrates. This can sometimes be the result of food insecurity, when you don’t have access to enough healthy food.
  • High alcohol intake
  • Sedentary lifestyle. You exercise fewer than three times a week.
  • Obesity or being overweight. Research shows this is a top reason for type 2 diabetes. Because of the rise in obesity among U.S. children, this type is affecting more teenagers.
  • Polycystic ovary syndrome (PCOS)
  • You're a member of an ethnicity that’s at higher risk: African Americans, Native Americans, Hispanic Americans, and Asian Americans are more likely to get type 2 diabetes than non-Hispanic whites.
  • You're a member of the LGBT community. Studies show that LGBT people are at higher risk to be overweight, smoke, drink alcohol, and use drugs, which are all risk factors for diabetes. These behaviors may be linked to "minority stress" -- the day-to-day stresses faced by marginalized people. 
  • You're over 45 years old. Older age is a significant risk factor for type 2 diabetes. The risk of type 2 diabetes begins to rise significantly around age 45 and rises considerably after age 65.
  • You’ve had an organ transplant. After an organ transplant, you need to take drugs for the rest of your life so your body doesn’t reject the donor organ. These drugs help organ transplants succeed, but many of them, such as tacrolimus (Astagraf, Prograf) or steroids, can cause diabetes or make it worse.
  • Impaired glucose tolerance. Prediabetes is a milder form of this condition. It can be diagnosed with a simple blood test. If you have it, there’s a strong chance you’ll get type 2 diabetes.
  • Family history. You have a parent or sibling who has diabetes. 

A proper diet and healthy lifestyle habits, along with medication, can help you manage type 2 diabetes the same way you manage other areas of your life. Be sure to seek the latest information on this condition as you become your own health advocate.

To understand why insulin is important, it helps to know more about how your body uses food for energy. Your body is made up of millions of cells. To make energy, these cells need food in a very simple form. When you eat or drink, much of the food is broken down into a simple sugar called glucose. It moves through your bloodstream to these cells, where it provides the energy your body needs for daily activities.

Insulin and other hormones control the amount of glucose in your bloodstream. Your pancreas is always releasing small amounts of insulin. When the amount of glucose in your blood rises to a certain level, the pancreas will release more insulin to push more glucose into the cells. This causes the glucose levels in the blood (blood glucose levels) to drop.

To keep blood glucose levels from getting too low (hypoglycemia, or low blood sugar), your body signals you to eat and releases some glucose from the stores kept in the liver. It also tells the body to release less insulin.

People with diabetes either don't make insulin or their body's cells can no longer use their insulin. This leads to high blood sugars. By definition, diabetes is:

  • A blood glucose level of greater than or equal to 126 milligrams per deciliter (mg/dL) of blood after an 8-hour fast
  • A non-fasting glucose level greater than or equal to 200 mg/dL, along with symptoms of diabetes
  • A glucose level greater than or equal to 200 mg/dL on a 2-hour glucose tolerance test
  • A1c greater than or equal to 6.5%. Unless the person is having obvious symptoms of diabetes or is in a diabetic crisis, the diagnosis must be confirmed with a repeat test.

Show Sources


American Diabetes Association: "Insulin and Low Blood Glucose," "Stomach Fat and Insulin Resistance," "Diabetes Risk Calculator;" "The Dangerous Toll of Diabetes;" "Diabetes Statistics." 

National Diabetes Information Clearinghouse: "Am I at Risk for Type 2 Diabetes?" "Your Guide to Diabetes: Type 1 and Type 2."

Diabetologia: “The threshold for diagnosing impaired fasting glucose: a position statement by the European Diabetes Epidemiology Group.”

Journal of the American College of Cardiology: “Comparison of the 1997 and 2003 American Diabetes Association Classification of Impaired Fasting Glucose: Impact on Prevalence of Impaired Fasting Glucose, Coronary Heart Disease Risk Factors, and Coronary Heart Disease in a Community-Based Medical Practice.”

American Diabetes Association (ADA): "Type 2 Diabetes," "Diabetes Risk Test."

National Heart, Lung, and Blood Institute: "Framingham Heart Study." 

Diabetes Care: “Obesity, inactivity, and the prevalence of diabetes and diabetes-related cardiovascular comorbidities in the U.S., 2000-2002.”

The New England Journal of Medicine: “A Toggle for Type 2 Diabetes?”

Lancet: “Type 2 diabetes: principles of pathogenesis and therapy.”

Circulation: “Trends in the Incidence of Type 2 Diabetes Mellitus From the 1970s to the 1990s: The Framingham Heart Study.”

CDC: “About Chronic Disease.”

Feeding America: “Child Nutrition Programs.”

Food Research and Action Center: “Hunger & Health: The Impact of Poverty, Food Insecurity, and Poor Nutrition on Health and Well-Being.”

Office of Disease Prevention and Health Promotion: “Food Insecurity.”

U.S. Department of Agriculture: “Food Security in the U.S.: Measurement,” “Definitions of Food Insecurity.”

National Kidney Foundation website.

United Network for Organ Sharing website.

United Network for Organ Sharing's "Transplant Living" website.

U.S. Department of Health and Human Services: "Partnering with Your Transplant Team: The Patient's Guide to Transplantation, 2004."

Bihl, G. Dialysis and Transplantation, 2004.

Carithers, R. Liver and Pancreas Transplantation, ACP Medicine, November 2003.

American Journal of Transplantation: “New Onset Diabetes Mellitus in Patients Receiving Calcineurin Inhibitors: A Systematic Review and Meta‐Analysis.”

Klassen, D. Renal Transplantation, ACP Medicine, January 2002.

Sievers, M. Transplant Trends, 2003.

View privacy policy, copyright and trust info