"Diabetes mellitus," more commonly referred to as "diabetes," is a condition that causes blood sugar to rise to dangerous levels: a fasting blood glucose of 126 milligrams per deciliter (mg/dL) or more.
Most of the food you eat is turned into glucose, or sugar, for your body to use for energy. The pancreas, an organ near the stomach, produces a hormone called insulin. This hormone is necessary for the body to be able to use sugar or glucose, the basic fuel for cells in the body. Insulin's role is to take sugar from the blood into the cells. When your body does not produce enough insulin and/or does not efficiently use the insulin it produces, sugar levels rise and build up in the bloodstream. When this happens, it can cause two problems:
How Diabetes Develops
- Right away, the body's cells may be starved for energy.
- Over time, high blood glucose levels may damage the eyes, kidneys, nerves or heart.
Types of DiabetesThere are two main types of diabetes: type 1 diabetes and type 2 diabetes. Both types may be inherited in genes, so a family history of diabetes can significantly increase a person's risk of developing the condition.
Type 1 Diabetes
Type 1 diabetes is a serious condition that occurs when the pancreas makes little or no insulin. Without insulin, the body is unable to take the glucose (blood sugar) it gets from food into cells to fuel the body. So without daily injections of insulin, people with type 1 diabetes won't survive. For that reason, this type of diabetes is also referred to as insulin-dependent diabetes.
Type 1 diabetes was previously known as juvenile diabetes because it's usually diagnosed in children and young adults. However, this chronic, lifelong disease can strike at any age, and those with a family history of it are particularly at risk.
Health Risks for Type 1 Diabetes
During the development of type 1 diabetes, the body's immune system attacks certain cells (called beta cells) in the pancreas. Although the reasons this occurs are still unknown, the effects are clear. Once these cells are destroyed, the pancreas produces little or no insulin, so the glucose stays in the blood. When there's too much glucose in the blood, especially for prolonged periods, all the organ systems in the body suffer long-term damage. Learn more about the health consequences of diabetes and how to treat it.
Type 2 Diabetes
Type 2 diabetes is the most common form of diabetes. Historically, type 2 diabetes has been diagnosed primarily in middle-aged adults. Today, however, adolescents and young adults are developing type 2 diabetes at an alarming rate. This correlates with the increasing incidence of obesity and physical inactivity in this population, both of which are risk factors for type 2 diabetes.
This type of diabetes can occur when:
- The body develops "insulin resistance" and can't make efficient use of the insulin it makes, and
- The pancreas gradually loses its capacity to produce insulin.
Precursors to DiabetesIn addition to full-blown diabetes mellitus, there are precursors to the disease:
Pre-diabetes is a condition in which fasting blood glucose (blood sugar) levels are higher than normal but have not quite reached the 126 milligrams/deciliter (mg/dL) threshold considered to be full-blown diabetes.
Any of the following blood test results identify pre-diabetes:
- Impaired fasting glucose (IFG): A person is considered to have IFG with a fasting blood glucose ranging from 100 to 125 mg/dL.
- Impaired glucose tolerance (IGT): Individuals with IGT have a fasting glucose less than 126 mg/dL and a glucose level between 140 and 199 mg/dL two hours after taking an oral glucose tolerance test.
- Higher than normal A1C: A person is considered to have an abnormal A1C level between 5.7-6.4%. The A1C test measures your average blood glucose control for the past 2 to 3 months.
The American Heart Association estimates that 81.5 million Americans 20 years and older have pre-diabetes. People with IFG and IGT are at increased risk for developing type 2 diabetes, heart disease and stroke. Long-term damage to the cardiovascular system may occur while a person has pre-diabetes, and a recent study indicates that pre-diabetes more than doubles the risk of death due to heart attack.*
* Circulation, July 10 2007; doi:10.1161/CIRCULATIONAHA.106.685628
Both type 2 diabetes and pre-diabetes usually result from insulin resistance.
Insulin resistance, which is a condition that affects more than 60 million Americans, occurs when the body can't use insulin efficiently. To compensate, the pancreas releases more and more insulin to try to keep blood sugar levels normal. Gradually, the insulin-producing cells in the pancreas become defective and ultimately decrease in total number. As a result, blood sugar levels begin to rise, causing pre-diabetes and, eventually, type 2 diabetes to develop.
When a fasting individual has too much glucose in the blood (hyperglycemia) or too much insulin in the blood (hyperinsulinemia), it indicates a person may have insulin resistance.
Health Risks of Insulin Resistance
People with insulin resistance are at greater risk of developing type 2 diabetes. They also are more likely to have too much LDL ("bad") cholesterol, not enough HDL ("good") cholesterol, and high triglycerides, which cause atherosclerosis.
Untreated diabetes can lead to many serious medical problems, including heart disease and stroke. That's why it's important to be aware of the symptoms as well as the risk factors and to take appropriate steps to prevent and treat insulin resistance and diabetes.
This content was last reviewed on 6/28/2012.