What are the causes of diabetes type 2?

The food we eat is broken down into many components that our bodies use for different purposes. Glucose (a type of sugar) is one of these components that's an important source of energy for our cells. It’s also the main source of fuel for our brains. In order for the body's cells to use glucose, the body needs insulin. Special cells in our pancreas, called beta cells, produce insulin. People with type 2 diabetes aren't able to make enough insulin or aren't able to properly use the insulin their bodies produce. Without enough insulin, glucose stays in the bloodstream, causing high blood sugar levels.

Type 2 diabetes is the most common type of diabetes: More than 90% of adults diagnosed with diabetes have type 2 diabetes. Many factors can contribute to developing type 2 diabetes, such as genetics, age, other diseases, and things you can control like lifestyle choices.

People with certain genetic makeups are more likely to develop type 2 diabetes, including those who have:

• Genes that make it more difficult for the pancreas to make insulin
• A particular version of a certain gene that releases less insulin after consuming glucose

Genetic makeup is hereditary, which means that it is passed on from parents to their children. This may help explain why a person with a first-degree relative (biological father, mother, sister or brother) who has type 2 diabetes is five to 10 times more likely to develop type 2 diabetes.

Also, if you are of a certain racial or ethnic group, you may be more likely to develop type 2 diabetes. Some genes that are more common in these groups are known to be linked with the disease. Diabetes is more common in people who are African American, Hispanic/Latino, American Indian, Asian American and Pacific Islander.

You are more likely to develop type 2 diabetes if you are age 45 or older. This is because as you get older, your body may become more resistant to insulin. This is especially true if your genetic makeup already puts you at risk for type 2 diabetes.

Certain diseases that change how your body produces hormones, such as Cushing's syndrome and hyperthyroidism, can make you resistant to insulin. This can lead to type 2 diabetes.

During pregnancy, some women develop gestational diabetes. This is a type of diabetes that occurs only during pregnancy when the hormones made by the placenta cause insulin resistance. Weight gain and decreased physical activity during pregnancy also affect the body's ability to make insulin. This can then lead to type 2 diabetes soon or years after the baby is born.

Diseases that affect your pancreas can also lead to type 2 diabetes. Pancreatitis and pancreatic cancer cause damage to insulin-producing beta cells, which can result in diabetes.

Injury to or loss of your pancreas, such as from an accident, can also lead to type 2 diabetes. 

Certain medications used to treat other conditions, such as hypertension (high blood pressure), seizures, human immunodeficiency virus (HIV), pneumonia and high cholesterol, can lead to type 2 diabetes. These medicines can affect beta cells or alter the way insulin works in your body. However, the benefit of these medications is much greater than the risk of type 2 diabetes. It is important that you consult with your healthcare provider or pharmacist before stopping any of your prescribed medications.

If you are overweight or obese, you are more likely to develop type 2 diabetes. This is because the extra weight can cause your body to become resistant to insulin. The location of the extra body fat is also an important factor. Having more fat around your midsection has been found to be related to insulin resistance. In fact, type 2 diabetes is related to obesity 80% of the time.

In 2019, the American Diabetes Association shared a study involving people in the early stages of the disease. The study found that 36% of those who participated in an intensive weight management program had their blood sugar return to normal, non-diabetes levels after two years. This was without using type 2 diabetes medications. 

Similarly, if you do not exercise regularly, you could be at risk for type 2 diabetes. Being physically inactive could lead to weight gain, especially when combined with poor eating habits. The Centers for Disease Control and Prevention's (CDC) National Diabetes Prevention Program reports that people who lost 5% to 7% of their body weight and added 150 minutes of exercise per week reduced their risk of type 2 diabetes by up to 58% (71% for people over 60 years old).

For more information on ways to reduce your risk of type 2 diabetes or how to maintain a healthier lifestyle once you're diagnosed, check out the CDC's National Diabetes Prevention Program online.

Clinically reviewed and updated June 2024.