Type 1 diabetes, previously known as juvenile diabetes, is the most severe form of the disease. About 5% of people who have diabetes have type 1 diabetes, or insulin-dependent diabetes. Type 1 diabetes has also been called juvenile diabetes becuse it usually develops in children and teenagers. But people of all ages can develop type 1 diabetes.  

In type 1 diabetes, the body’s immune system attacks the insulin-producing islet cells in the pancreas. The islet cells sense glucose in the blood and produce the right amount of insulin to normalize blood sugars. This attack on the body's own cells is known as autoimmune disease. Scientists are not sure why the autoimmune attack happens.

But once the insulin-producing cells are destroyed, a person can no longer produce their own insulin. Without insulin, there is no “key.” So, the sugar stays in the blood and builds up. As a result, the body’s cells starve. And, if left untreated, high blood sugar levels can damage eyes, kidneys, nerves, and the heart, and can also lead to coma and death. 

So type 1 diabetes must be treated through a daily regimen of insulin therapy. (https://www.diabetesresearch.org/what-is-diabetes)

The onset of type 1 diabetes happens very quickly. The following symptoms may appear suddenly and are too severe to overlook:
•Increased thirst
•Increased urination (bed-wetting may occur in children who have already been toilet trained)
•Rapid and unexplained weight loss
•Extreme hunger
•Extreme weakness or fatigue
•Unusual irritability
•Blurred vision
•Nausea, vomiting and abdominal pain
•Unpleasant breath odor
•Itchy skin

(https://www.diabetesresearch.org/what-is-diabetes)

The most common form of diabetes is called type 2 diabetes, or non-insulin dependent diabetes. About 90% of people with diabetes have type 2. Type 2 diabetes is also called adult onset diabetes, since it typically develops after age 35. However, a growing number of younger people are now developing type 2 diabetes.  

People with type 2 diabetes are able to produce some of their own insulin. Often, it’s not enough. And sometimes, the insulin will try to serve as the “key” to open the body’s cells, to allow the glucose to enter. But the key won’t work. The cells won’t open. This is called insulin resistance. Type 2 diabetes is typically tied to people who are overweight with a sedentary lifestyle. (https://www.diabetesresearch.org/what-is-diabetes)