What Causes Diabetes?

Reviewed by: HU Medical Review Board

Diabetes is a disease that impacts how the body uses glucose, a sugar that is the primary source of energy for the body. Normally, you eat and get glucose from the food into your bloodstream, or your liver makes glucose. Your pancreas makes insulin, a hormone that helps get the glucose into the cells of your body. The cells then use glucose to fuel your body.1,2

If you have type 2 diabetes, your body cannot make insulin or use insulin the way it should. The glucose cannot enter your cells the way it should, leaving the glucose in your bloodstream. This increases glucose (sugar) levels in your blood. Increased blood sugar leads to many problems in the body and makes you sick.1

Type 1 and type 2 diabetes, the 2 most common forms of diabetes, are characterized by increased blood sugar. However, the causes of high blood sugar in these forms of diabetes are quite different.1,2

What is type 1 diabetes?

Type 1 diabetes used to be called juvenile diabetes or insulin-dependent diabetes. In type 1 diabetes, the body cannot make insulin. Type 1 diabetes is an autoimmune disease in which the immune system malfunctions and attacks beta cells. Beta cells produce insulin, which allows cells of the body to use glucose (sugar). The glucose stays in the bloodstream and cannot enter the cells and be used as energy.1,2

A person with type 1 diabetes has abnormally high blood glucose because their body no longer produces enough insulin. This leads to health problems, some of which are life-threatening.1,2

Causes of type 1 diabetes

Doctors are not sure of the exact cause of type 1 diabetes. It is an autoimmune disorder where the body attacks its healthy cells in the pancreas. Doctors think that genes and family history are factors that cause type 1 diabetes.1

What is type 2 diabetes?

In type 2 diabetes, the pancreas still makes insulin. However, insulin does not do its job effectively, leading to a build-up of glucose (sugar) in the bloodstream. In response, the pancreas makes more insulin to get the glucose into the cells. Eventually, the pancreas gets worn out from working too hard, leading to increased blood sugar levels.2,3

Causes of type 2 diabetes

Type 2 diabetes is the most common form of diabetes. It is caused by several things, including lifestyle factors, insulin resistance, and genes.2,3

Environment and lifestyle factors

Several environmental and lifestyle factors have been identified as playing an essential role in causing type 2 diabetes, including:3,4

  • Increased weight and inactivity. Being overweight or obese increases the risk of developing type 2 diabetes. Excess weight, especially fat around your abdomen, decreases the ability of your body to use insulin. A lack of exercise also decreases the body’s ability to use insulin.
  • Smoking. Smoking increases your risk of developing type 2 diabetes by 30 to 40 percent. Chemicals from cigarettes harm the cells in your body, affecting their normal function. Impaired cellular function leads to inflammation, which can decrease the effectiveness of insulin.

Insulin resistance

Insulin resistance happens when cells in your muscles, fat, and liver do not easily take up glucose from your blood because the cells do not respond well to insulin. Your pancreas continues to make more insulin to help with the process. Insulin resistance is often caused by excess weight and inactivity.5

Family history and genes

Your family history plays a strong role in the development of type 2 diabetes. Studies have shown that type 2 diabetes can run in families, and specific genes can lead to type 2 diabetes development. However, inheriting a genetic predisposition to diabetes does not mean you will develop type 2 diabetes. Your environmental and lifestyle factors may cause you to develop the disease. For example, obesity and inactive lifestyles may be passed down from one generation to the next.6

It may be hard to know if your type 2 diabetes diagnosis is because of genetics or lifestyle choices. Chances are, it may be a combination of both. Understanding how lifestyle factors impact type 2 diabetes, can help you prevent or control the disease.6

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