NEW YORK (Reuters Life!) More than half of Americans will have diabetes or be prediabetic by 2020 at a cost to the US health care system of $3.35 trillion if current trends go on unabated, according to analysis of a new report.

The report by health insurer UnitedHealth Group Inc said diabetes and prediabetes will account for an estimated ten percent of total health care spending by the end of the decade at an annual cost of almost $500 billion up from an estimated $194 billion this year.

The average annual health care costs in 2009 for a person with diabetes were about $11,700 compared with about $4,400 for the non-diabetic public, according to new data in the report drawn from ten million UnitedHealthcare members.

The average annual cost nearly doubles to $20,700 for a person with complications related to diabetes, the report said.

Complications related to diabetes can include heart and kidney disease, nerve damage, blindness and circulatory problems that can lead to wounds that will not heal and limb amputations.

Diabetes, which is reaching epidemic proportions and is one of the fastest-growing diseases in the United States, currently affects about 26 million Americans. Another 67 million Americans are estimated to have prediabetes, which may not have any obvious symptoms.

More than 60 million Americans are unaware that they have the condition, according to UnitedHealth.

People with prediabetes have higher than normal blood sugar levels, but not yet high enough to be diagnosed as diabetes. Prediabetics often have other risk factors, such as overweight, high blood pressure and high cholesterol.

The 52-page report also focuses on the growing obesity epidemic which is a leading cause of diabetes.