Recent studies show that three out of 10 Americans do not know that they have diabetes. Some doctors do not know if patients have the disease either.

The study published in Annals of Internal Medicine, conducted by chair of the Emory University Department of Global Health Dr. Carlos del Rio, chair of the Emory University Department of Global Health, and other Emory University scientists, shows that many Americans have a lax attitude toward diabetes.

"Sometimes, people think 'serious' means things that kill you right away," del Rio told Yahoo! Health. "But, the reality is, I would be more concerned about diabetes than Ebola." 

Diabetes may not be an instant killer, but it is the seventh leading cause of death in the United States. Over time, the disease can lead to amputations and blindness.

The study proved that about 28.4 million American adults had diabetes in 2012 and about 8 million of those had not been diagnosed.

What was most alarming about the study is that two-thirds of undiagnosed diabetics had seen a doctor at least twice in the past year. It is surprising that so many people go undiagnosed because diabetes gets worse the longer it goes untreated.

"Once the disease sets in, it's really progressive," study co-author Mohammed Ali, an assistant professor of global health at Emory University, told Yahoo! Health.

"Diabetes is the silent killer," said del Rio. "It may be slow in some cases, but it leads to really disabling and often fatal complications."

Ali said if you catch and control diabetes early, "patients are very likely to do well, in terms of delaying the onset of all these horrendous complications, preserving their quality of life."

Yet, doctors do not have clear clues to suggest early testing on the disease unless weight, family history and lifestyle are taken into consideration.

Doctors in the U.S. usually pay attention to specific symptoms rather than regular routines.

The study also showed that younger people were more likely to go undiagnosed because they usually go to the doctor when they feel sick.