You may think you already know the signs of diabetes: You're thirsty all the time, you feel exhausted 24/7 and/or you're constantly running to the bathroom. Yet a surprising number of Americans have abnormally high blood-sugar (glucose) levels but don't know it. The signs can be so subtle—or altogether absent—that the problem goes undetected, yet it increases the risk for heart disease and other serious health problems. As more and more of us pack on extra pounds, the incidence of diabetes and its recently defined precursor, pre-diabetes, is soaring in the United States.

What it is

Diabetes is a disease in which levels of blood glucose, also called blood sugar, are above normal. People with diabetes have problems converting food to energy. Normally, after a meal, the body breaks food down into glucose, which the blood carries to cells throughout the body. Cells use insulin, a hormone made in the pancreas, to help them convert blood glucose into energy.

People develop diabetes because the pancreas does not manufacture enough insulin or because the cells in the muscles, liver, and fat do not use insulin properly, or both. As a result, the amount of glucose in the blood increases while the cells are starved of energy. Over the years, high blood glucose, also called hyperglycemia, damages nerves and blood vessels, which can lead to complications such as heart disease, stroke, kidney disease, blindness, nerve problems, gum infections, and amputation.