Three major diabetes types can develop: Type 1, type 2, and gestational diabetes.

Type I diabetes: Also known as juvenile diabetes, this type occurs when the body fails to produce insulin. People with type I diabetes are insulin-dependent, which means they must take artificial insulin daily to stay alive.

Type 2 diabetes: Type 2 diabetes affects the way the body uses insulin. While the body still makes insulin, unlike in type I, the cells in the body do not respond to it as effectively as they once did. This is the most common type of diabetes, according to the National Institute of Diabetes and Digestive and Kidney Diseases, and it has strong links with obesity.

Gestational diabetes: This type occurs in women during pregnancy when the body can become less sensitive to insulin. Gestational diabetes does not occur in all women and usually resolves after giving birth.

Less common types of diabetes include monogenic diabetes and cystic fibrosis-related diabetes.

Click here to learn more about type I diabetes.

Prediabetes

Doctors refer to some people as having prediabetes or borderline diabetes when blood sugar is usually in the range of 100 to 125 milligrams per deciliter (mg/dL).

Normal blood sugar levels sit between 70 and 99 mg/dL, whereas a person with diabetes will have a fasting blood sugar higher than 126 mg/dL.

The prediabetes level means that blood glucose is higher than usual but not so high as to constitute diabetes.

People with prediabetes are, however, at risk of developing type 2 diabetes, although they do not usually experience the symptoms of full diabetes.

The risk factors for prediabetes and type 2 diabetes are similar. They include:

• being overweight
• a family history of diabetes
• having a high-density lipoprotein (HDL) cholesterol level lower than 40 mg/dL or 50 mg/dL
• a history of high blood pressure
• having gestational diabetes or giving birth to a child with a birth weight of more than 9 pounds
• a history of polycystic ovary syndrome (PCOS)
• being of African-American, Native American, Latin American, or Asian-Pacific Islander descent
• being more than 45 years of age
• having a sedentary lifestyle

If a doctor identifies that a person has prediabetes, they will recommend that the individual makes healthful changes that can ideally stop the progression to type 2 diabetes. Losing weight and having a more healthful diet can often help prevent the disease.

How insulin problems develop

Doctors do not know the exact causes of type I diabetes. Type 2 diabetes, also known as insulin resistance, has clearer causes.

Insulin allows the glucose from a person’s food to access the cells in their body to supply energy. Insulin resistance is usually a result of the following cycle:

1. A person has genes or an environment that make it more likely that they are unable to make enough insulin to cover how much glucose they eat.
2. The body tries to make extra insulin to process the excess blood glucose.
3. The pancreas cannot keep up with the increased demands, and the excess blood sugar starts to circulate in the blood, causing damage.
4. Over time, insulin becomes less effective at introducing glucose to cells, and blood sugar levels continue to rise.

In the case of type 2 diabetes, insulin resistance takes place gradually. This is why doctors often recommend making lifestyle changes in an attempt to slow or reverse this cycle.