The amount of sugar in your blood naturally fluctuates, but within a narrow range. Following an overnight fast, most people have lev­els between 70 and 110 milligrams of glucose per deciliter of blood (mg/ dL). This concentration - equal to about 1 teaspoon of sugar in a gallon of water - is considered normal.

Anyone whose blood sugar is consistently 126 mg/ dL or higher after fasting, he/she has diabetes. At one time, a diagnosis of diabetes required a blood sugar level of 140 mg/dL or higher. The standard was lowered in 1997 after a committee of the American Diabetes Association (ADA) reviewed the results of 15 years of diabetes research. The committee found that by the time blood sugar reaches 140 mg/ dL, some people already have organ damage. The ADA concluded it's best to diagnose and treat diabetes earlier, before complications develop.

If anyone’s blood sugar level measures between 111 and 125 mg/ dL, he/she has impaired fasting glucose, commonly referred to as bor­derline diabetes or prediabetes. Like diabetes, borderline diabetes shouldn't be taken lightly. It's a sign that he/she is at high risk of developing the disease and that he/she should see his/her doctor regu­larly and take steps to control his/her blood sugar.

Perhaps you've heard some of the common myths about diabetes ­that you can catch it from someone else, or that it comes from eat­ing too much sugar. Not true. Researchers don't fully understand why some people develop the disease and others don't. It's clear though that your lifestyle and certain health conditions increase your risk.

Family history: Your chance of developing either type 1 or type 2 diabetes increases if someone in your immediate family has the disease, whether that person is a parent, brother or sister. It's clear that genetics playa role in the disease, but exactly how certain genes may cause diabetes is still unknown.

Scientists are looking for genes that may be associated with type 1 and 2 diabetes. In fact, they have found some genetic mark­ers for type 1 diabetes, which means it's possible to screen relatives of people with type 1 diabetes to see if they also are at risk of the disease. In a study sponsored by the National Institute of Diabetes and Digestive and Kidney Diseases, relatives at risk of type 1 dia­betes are being treated with low doses of either insulin or an oral medication to see if the drugs may prevent the disease.

Weight: Being overweight is one of the most obvious risk factors for diabetes. More than 8 out of 10 people with type 2 diabetes are overweight. A recent study sponsored by the Centers for Disease Control and Prevention found that among Americans who are obese, 13.5 percent have diabetes, compared with 3.5 percent of Americans at a normal weight.

The more fatty tissue you have, the more resistant your muscle and tissue cells become to your own insulin. This is especially true if excess weight is concentrated around your abdomen. It's as though fat blocks insulin from unlocking your cells to let the sugar inside.

Many people with diabetes who are overweight often can improve their blood sugar simply by losing weight. In some cases that's all it takes to bring their blood sugar back into a normal range. Even small weight loss can have beneficial effects, reducing blood sugar levels or allowing diabetes medications to work better.

Inactivity: The less active you are, the greater your risk of devel­oping diabetes. Physical activity helps you control your weight, uses up blood sugar as energy, makes cells more sensitive to insulin, increases blood flow and improves circulation in even the smallest blood vessels. It may decrease your risk of developing type 2 diabetes by up to 50 percent.

Another advantage of exercise is that it adds muscle mass. Normally, between 70 percent to 90 percent of your blood sugar is absorbed into your muscles. A reduction of muscle mass - which commonly takes place as you grow older or as you become less physically active - can severely reduce the available storage space for blood sugar. With nowhere to go, sugar remains in your bloodstream.

Age: Your risk of type 2 diabetes increases as you grow older, especially beyond the age of 45. Part of the reason is that as people grow older, they tend to become less physically active, lose muscle mass and gain weight.

Recent years, however, have seen a dramatic rise in diabetes among people in their 30s and 40s. And although the prevalence of type 1 diabetes has remained steady, more children and teenagers are being diagnosed with type 2 diabetes.