There’s a Third Type of Diabetes—and Doctors Are Misdiagnosing It as Type 2

If you have a history of pancreatic disease and have recently been diagnosed with type 2 diabetes, you may actually have a new form of the disease called type 3c diabetes. What you or your doctor don't know may affect how well your disease is controlled.

DiabetesSyda Productions/ShutterstockThere are many surprising facts about type 2 diabetes, including the fact that sometimes it’s actually something else. Say hello to a new form of diabetes. It’s called type 3c diabetes and may be commonly mistaken for type 2 diabetes, the form of the disease most closely linked to obesity, a new study suggests.

As a result, many people with type 3c diabetes may not be getting the care they need to keep the eventual consequences of diabetes, such as eye, nerve, and kidney damage, at bay, the researchers warn in Diabetes Care.

Type 3c diabetes follows disease of the pancreas and is also called pancreatogenic diabetes, explains study author Simon de Lusignan, BSc, MB BS, MSc, MD(Res), professor of primary care and clinical informatics, the chair in health care management, and head of the department of clinical and cxperimental medicine at University of Surrey in Guildford, UK. “After pancreas disease, it is possible to develop diabetes. The people who do should be labeled type 3c. This is often not thought about, and they are instead labeled as type 2.”

Some 88 percent of people who had type 3c diabetes in the study were misdiagnosed as having type 2 over a 10-year period. Put another way: Just 3 percent of the people in the study were correctly identified as having type 3c diabetes.

The pancreas is intricately involved in all forms of diabetes. Located behind the lower part of the stomach, this organ is charged with producing insulin, the hormone that helps the body use glucose (blood sugar) in foods for energy. It plays a crucial role in the differences between type 1 and type 2: In type 1 diabetes, the pancreas stops producing insulin altogether. In type 2 diabetes, your body does not use insulin properly. In these cases, the pancreas cranks up insulin production to make up for the shortfall, but can’t keep pace after a while, according to the American Diabetes Association.

Enter type 3c.

This form of the disease shares some features with type 1 diabetes, namely a need for insulin relatively soon after diagnosis. It also bears some similarities to type 2 diabetes, including similar ages at diagnosis and some shared risk factors, such as obesity.

Type 3c diabetes is more common than type 1 diabetes, but less common than type 2, Lusignan says. It is also different than type 3 diabetes, which some people in the medical field say is actually Alzheimer’s disease.

“The key risk factor for type 3c diabetes is pancreatitis—both acute and chronic pancreatitis,” he says. Pancreatitis is an inflammation of the pancreas and can also be a sign of pancreatic cancer. “People with the disease cystic fibrosis, and people who have had pancreatic surgery are also at risk, though they were not the subjects of our research.”

There may be some health consequences if a person with type 3c is told they have type 2 instead.

“We found that whereas 5 percent of people with type 2 diabetes are treated with insulin in five years, 21 percent of people who had acute pancreatitis and nearly half of those who had chronic pancreatitis were on insulin,” Lusignan says. “If you identify the type of diabetes correctly, you can stratify your treatment and expectations accordingly.”

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People with type 3c diabetes are also more likely to have poor blood sugar control compared to their counterparts with type 2, the study showed. This may mean they need to be followed more closely and told that they are more likely to need insulin so that they don’t feel like they did something wrong when, and if, the time comes.

“The paper is a great reminder that though we lump diabetes into type 1 [and] type 2, a few other types exist. In fact people can have overlapping forms and there are probably almost as many types of diabetes as there are people,” says John B. Buse, MD, PhD, the Verne S. Caviness distinguished professor, chief of the division of endocrinology and director of the diabetes center at the University of North Carolina at Chapel Hill School of Medicine. “You may share many features with others with diabetes but your experience of diabetes is likely to be relatively unique. “

That said, “it’s feasible that some people in the new study have ‘mixed-type’ diabetes,” he speculates. “Though there are cases of classical pancreatic diabetes that are relatively uncommon, this type of study is mixing in people who probably have some type 2 diabetes stuff going on and evidence of pancreatic damage as well.”

Yes, type 3c “is different from run-of-the-mill type 2 diabetes, but how different depends on how much pancreatic damage or disease,” Buse says.

“If someone has diabetes and they have a history of pancreatic damage, disease or surgery, they should make sure that their providers are aware of it,” he says. But, he adds, “if their diabetes is well controlled and they do not have any discomforting symptoms, they are OK either way.”

If you have any type of diabetes, tweaking these behaviors improves control over your blood sugar.

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