The Family Health Guide

Preventing diabetes: Understanding and diagnosing the disease

Preventing diabetes: Understanding and diagnosing the disease

About 21 million Americans have diabetes, but a third of them don't know it. That means 7% of American adults are diabetic and many more have impaired fasting glucose, which is better known as pre-diabetes. These are worrisome figures, but the explosive increase in the disease is more worrisome still. The prevalence of diabetes increased by about 40% during the 1990s and rose by another 8% in the year 2000. And every projection indicates that it will continue to grow in the future.

Since the disease becomes more common as people age, it's tempting to ascribe the surge in diabetes to our aging population. That's part of the explanation — but only a small part. In fact, the greatest increase in diabetes has occurred in children and adolescents.

Does it matter?

It sure does. Men with diabetes are about twice as likely to develop heart disease as those without diabetes. In addition, diabetes is a major cause of kidney failure, loss of vision, peripheral artery disease, leg amputation, and cognitive impairment.

All in all, diabetes shortens life expectancy by about 13 years; no wonder it's the sixth leading cause of death in the United States, taking about 300,000 lives annually.

What is diabetes?

To understand diabetes, you should first understand how your body handles glucose, the sugar that fuels your metabolism. After you eat, your digestive tract breaks down carbohydrates into simple sugars that are small enough to be absorbed into your bloodstream. Glucose is the most important of these sugars, and it's an indispensable source of energy for your body's cells. But to provide that energy, it must travel from your blood into your cells.

Insulin is the hormone that unlocks the door to your cells. When your blood glucose levels rise after a meal, the beta cells of your pancreas spring into action, pouring insulin into your blood. If you produce enough insulin and your cells respond normally, your blood sugar level drops as glucose enters the cells, where it is burned for energy or stored in your liver as glycogen for future use. A mild elevation of blood sugar doesn't produce any symptoms. But even mild diabetes is dangerous, since it damages blood vessels and other vital organs. When sugar levels get higher, they produce symptoms that may include fatigue and blurred vision. Excess sugar spills into the urine, taking water with it. This produces excessive urination and dehydration, which lead to increased thirst. Excess hunger is another symptom, and weight loss may develop despite a hearty appetite. This happens because while the blood has too much sugar, the cells don't get enough.

The three types of diabetes

The name diabetes encompasses three different disorders that are all marked by abnormally high blood sugar levels.

Type 1 diabetes was formerly known as juvenile or insulin-dependent diabetes. It usually begins abruptly before the age of 20, often with a critical rise in blood sugar levels. The disease is caused by a combination of genetic abnormalities and environmental triggers that cause the body's immune system to attack the pancreas, destroying its ability to produce insulin. Type 1 diabetes is the most severe form of the disease, but it accounts for only about 5% of cases in the United States. Lifelong insulin therapy is mandatory.

Type 2 diabetes was once called adult-onset or non-insulin-dependent diabetes. In most cases, the main problem is insulin resistance. The pancreas produces reasonable amounts of the hormone, but the body's tissues don't respond properly, so blood sugar levels are abnormally high. Oral medications can help many patients compensate for insulin resistance. But over time, the ability of the overtaxed pancreas to secrete insulin may run down, requiring insulin therapy.

Lifestyle factors are the major contributors to the disease, with obesity heading the list.

Gestational diabetes, which occurs during pregnancy, increases the risk of complications for mother and child. Blood sugar levels return to normal after delivery, but many women develop type 2 diabetes later in life.


The American Diabetes Association (ADA) has proposed a simple standard for the diagnosis of diabetes: a fasting blood sugar of 126 mg/dL or higher, providing the result is confirmed on a second test. Fasting blood sugars between 100 and 125 indicate impaired glucose tolerance, a milder condition that may lead to diabetes; levels below 100 are officially normal.

Although a fasting blood sugar of 126 is the standard for diagnosing diabetes, two other criteria are also available. Any blood sugar level above 200 suggests the diagnosis, even if it's obtained after eating.

A third way to evaluate diabetes is to see what percent of the oxygen-carrying hemoglobulin molecules in a person's red blood cells have glucose attached to them. When should you be tested for diabetes? It's most convenient when you're having a regular checkup, especially if you are already fasting for a cholesterol check. The ADA recommends a test every three years for people 45 or older. Individuals with risk factors such as being obese or overweight, having a diabetic parent or sibling, or having high blood pressure or high cholesterol levels should begin testing earlier and should have repeat tests as often as once a year. Diagnosing diabetes early is important because prompt and aggressive treatment can help ward off the often-deadly complications of the disease. But preventing it from developing in the first place is even better.

July 2007 update