What is diabetes?

What are the different types?

Diabetes mellitus, or diabetes, is a chronic metabolic disease characterized by:

  • high blood glucose, or hyperglycemia
  • impaired fat, carbohydrate and protein metabolism (the process in which the body breaks down food for energy).

Carbohydrates in food are broken down into glucose, a simple sugar, by the digestive tract. Glucose then enters the bloodstream and is transported to the organs as a source of energy. After a meal, blood glucose level rises, and the pancreas is triggered to release a hormone called insulin. The pancreas, an organ located behind the stomach, contains islets, a cluster of cells, called beta cells. These beta cells produce insulin and release it into the bloodstream. Insulin helps cells absorb glucose and use it as energy.


Diabetes develops due to abnormalities in this process: inadequate insulin secretion [the body doesn’t make enough insulin] and/or impaired response to insulin [the body cannot use insulin effectively]. As a result, glucose builds up in the blood and the cells “starved” [despite high levels of glucose already present in the blood]. The accumulation of glucose over time can lead to hyperglycemia, which can cause damage to vital organs and lead to serious complications.

Islets within the pancreas contain beta cells, which make insulin and release it into the blood.

There are three main types of diabetes:

  1. Type 1 diabetes
  2. Type 2 diabetes
  3. Gestational diabetes


Type 1 diabetes (T1D) is characterized by autoimmune destruction of ß-cells of the pancreas resulting in absolute deficiency of insulin secretion. Although T1D can affect people of any age, it accounts for ~5-10% of children and adolescence.

Treatment of T1D centers on the replacement of insulin for T1D patients that will help manage their condition. Without insulin, T1D patients will die. Genetic, environmental, and immunological factors contribute to the onset of this disease.

Type 2 diabetes (T2D) is characterized by the abnormalities in one or a combination of the following processes:
– relative insulin resistance
– impaired insulin production and secretion
– increased glucose production.

In T2D, muscle, liver and fat cells are unable to use insulin due to the above mentioned abnormalities. Therefore, the body makes more insulin to help glucose enter the cells and be used for energy. With time, the pancreas cannot meet the high demand of insulin and loses its ability to produce enough. The lack of insulin leads to hyperglycemia.

T2D accounts for ~90-95% of patients with diabetes and usually presents during adulthood; however, the incidence of adolescent onset of T2D is increasing. T2D is often associated with obesity, physical inactivity, family history of diabetes, history of gestational diabetes, and race.

Gestational diabetes (GDM) is a type of diabetes that develops only during pregnancy. During early pregnancy, hormones are released that require insulin to control blood glucose levels. If the demand for insulin is not met, women can develop GDM. GDM is classified as a slightly elevated blood glucose levels, whereas women with a substantially elevated blood glucose are known to have diabetes in pregnancy.

GDM affects 4% of all pregnant women in the 3rd trimester (24 weeks).

What is pre-diabetes?

Pre-diabetes is a condition of elevated blood glucose, higher than normal but not high enough for a diabetes diagnosis. This occurrence is also known as impaired glucose tolerance or impaired fasting glucose. People with pre-diabetes are at increased risk of developing type 2 diabetes and other complications. Maintaining healthy eating habits and modest physical exercise can help delay or prevent the development of type 2 diabetes by normalizing glucose tolerance.