Diabetes is a chronic condition that occurs when the body cannot produce enough insulin or effectively use the insulin it produces. There are two main types of diabetes: type 1 and type 2. Then there’s also gestational diabetes. These types of diabetes and their causes are discussed below.

Type 1 diabetes

Type 1 diabetes occurs when your immune system, the body’s system for fighting infection, attacks and destroys the insulin-producing beta cells of the pancreas. Scientists think type 1 diabetes is caused by genes and environmental factors, such as viruses, that might trigger the disease. Studies such as TrialNet are working to pinpoint causes of type 1 diabetes and possible ways to prevent or slow the disease..

Type 2 diabetes

Type 2 diabetes—the most common form of diabetes—is caused by several factors, including lifestyle factors and genes. These factors are considered below.

• A diet high in processed foods, sugar, and unhealthy fats
• High blood pressure
• A history of gestational diabetes
• Polycystic ovary syndrome (PCOS)
• A sedentary lifestyle
• An increased age
• A history of heart disease or stroke

Gestational diabetes

Scientists believe gestational diabetes, a type of diabetes that develops during pregnancy, is caused by the hormonal changes of pregnancy along with genetic and lifestyle factors.

• Insulin resistance
• Genes and family history

Other factors that risk getting diabetes

• Genetic mutations.
  • Monogenic diabetes is caused by mutations, or changes, in a single gene. These changes are usually passed through families, but sometimes the gene mutation happens on its own. Most of these gene mutations cause diabetes by making the pancreas less able to make insulin. The most common types of monogenic diabetes are neonatal diabetes and maturity-onset diabetes of the young (MODY).
  • Cystic fibrosis produces thick mucus that causes scarring in the pancreas. This scarring can prevent the pancreas from making enough insulin.
  • Hemochromatosis causes the body to store too much iron. If the disease is not treated, iron can build up in and damage the pancreas and other organs.
• Hormonal diseases.
  • Cushing’s syndrome occurs when the body produces too much cortisol—often called the “stress hormone.”
  • Acromegaly occurs when the body produces too much growth hormone.
  • Hyperthyroidism occurs when the thyroid gland produces too much thyroid hormone.
• Damage to or removal of the pancreas.
  • Pancreatitis, pancreatic cancer, and trauma can all harm the beta cells or make them less able to produce insulin, resulting in diabetes. If the damaged pancreas is removed, diabetes will occur due to the loss of the beta cells.
• Certain medicines.
  • niacin, a type of vitamin B3
  • certain types of diuretics, also called water pills
  • anti-seizure drugs
  • psychiatric drugs
  • drugs to treat human immunodeficiency virus (HIV NIH external link)
  • pentamidine, a drug used to treat a type of pneumonia External link
  • glucocorticoids—medicines used to treat inflammatory illnesses such as rheumatoid arthritis NIH external link, asthma NIH external link, lupus NIH external link, and ulcerative colitis
  • anti-rejection medicines, used to help stop the body from rejecting a transplanted organ

Statins, which are medicines to reduce LDL (“bad”) cholesterol levels, can slightly increase the chance that you’ll develop diabetes. However, statins help protect you from heart disease and stroke. For this reason, the strong benefits of taking statins outweigh the small chance that you could develop diabetes. If you take any of these medicines and are concerned about their side effects, talk with your doctor.

It is important to remember that while these factors can increase the risk of developing type 2 diabetes, they do not necessarily cause the condition. The exact cause of type 2 diabetes is still not fully understood and is likely a complex interplay of genetic and environmental factors.