You’ve probably heard of type 1 and type 2 diabetes. According to the Centers for Disease Control and Prevention (CDC), more than 34 million Americans have diabetes — but the actual number might be much higher. A 2015 study with mice indicates that diabetes might be underdiagnosed in older adults who don’t have overweight or obesity. While not an official classification of diabetes, researchers are calling this type 4 diabetes.

Type 4 diabetes isn’t an autoimmune condition like type 1 diabetes, and it’s not linked to weight like type 2 diabetes. Instead, this potential type of diabetes may be linked to the aging process. Research into this condition is ongoing, but scientists have already uncovered some connections.

Diabetes is often thought of as having two distinct types, though gestational diabetes is also quite common. All types of diabetes cause high blood sugar because your body has trouble producing insulin, a hormone that moves and stores sugar.

Most common types

  • Type 1 diabetes. Type 1 diabetes is most commonly diagnosed in children and teenagers. It’s an autoimmune condition. When you have type 1 diabetes, your immune system attacks the cells in your pancreas responsible for making insulin.
  • Type 2 diabetes. Type 2 diabetes happens when your body stops responding to the insulin your pancreas makes. Over time, your pancreas also stops producing enough insulin. It’s generally linked to a combination of genetic and lifestyle factors.
  • Gestational diabetes. This type of diabetes is a response to the hormonal changes that happen during pregnancy. The hormones made in the placenta can lower your body’s sensitivity to insulin. This may result in high blood sugar during pregnancy.

Type 1, type 2, and gestational diabetes are very common, but they’re not the only types of diabetes. There are several other types of diabetes, and a few that are not officially classified as types.

Specific diabetes due to other causes

  • Mature onset diabetes of the young (MODY). This type of diabetes occurs due to a genetic change, and runs in families. Children with the genetic change will often develop this form of diabetes by the time they are 25.
  • Neonatal diabetes. Neonatal diabetes is generally diagnosed in children under 6 months old. It’s an inherited condition that’s different from type 1 diabetes because it’s not an autoimmune condition. Instead, children with this condition are born with a genetic change that affects their ability to produce insulin.
  • Diabetes caused by other conditions. This type of diabetes is caused by conditions including cystic fibrosis, pancreatic cancer, or pancreatitis that damage the pancreas’ ability to produce insulin.
  • Steroid-induced diabetes. This type of diabetes can happen when you take steroids that affect hormone production in your body.

Other terms you may hear

While these aren’t official types of diabetes, you may sometimes hear these terms when talking about diabetes. They include:

  • Monogenic diabetes. This includes both MODY and neonatal diabetes, and refers to any type of diabetes that’s caused by genetic changes.
  • Type 3c diabetes. This is sometimes used to refer to diabetes caused by other conditions, such as cystic fibrosis and pancreatic cancer.
  • Latent autoimmune diabetes in adults (LADA). This is sometimes referred to as type 1.5 diabetes. Some experts think of it as a subtype of type 1 diabetes. While it is an autoimmune disease like type 1, LADA progresses more slowly. It’s often misdiagnosed as type 2 diabetes because you may still be able to produce insulin for some time.

Recent discussion of new types

Recently, some researchers have suggested that two additional types of diabetes might exist. These aren’t yet official diabetes types or diagnoses, but that might change as more information becomes available.

  • Type 3 diabetes. Type 3 diabetes is used to explain the theory that insulin resistance might cause Alzheimer’s disease, a form of dementia. A 2018 research review showed that people with type 2 diabetes are more likely to develop Alzheimer’s disease. Experts are still investigating this link.
  • Type 4 diabetes. Type 4 diabetes is the proposed term for diabetes caused by insulin resistance in older people who don’t have overweight or obesity. A 2015 study with mice suggested this type of diabetes might be widely underdiagnosed. This is because it occurs in people who aren’t overweight or obese, but are older in age.

Scientists are just beginning to study type 4 diabetes, so they don’t yet have a lot of concrete information about what causes it.

A 2015 study with mice showed that the condition referred to as type 4 diabetes is linked to an excess of immune cells called regulatory T cells. Researchers have a theory that this is linked to the aging process, but studies in humans are still needed.

Type 4 diabetes has many of the same symptoms as other types of diabetes. However, because it generally appears in people with a moderate weight, doctors may not suspect diabetes. Common symptoms include:

Many of these symptoms are also linked to other conditions and might not always indicate diabetes.

It’s a good idea to make an appointment with a medical professional if you’ve been experiencing any of these symptoms. A doctor can review your symptoms and order any tests they think are needed.

Type 4 diabetes isn’t officially a diagnosis yet. Many things about this condition, including treatment, are still being studied. However, according to Salk Center FAQ, researchers are hopeful that they will be able to develop an antibody medication. This could help reduce the number of regulatory T cells in the body and treat type 4 diabetes.

Until this medication is developed, your doctor will probably treat type 4 diabetes with the same medications prescribed to people with type 2 diabetes.

Many of the lifestyle recommendations for people with type 2 diabetes aren’t effective for people with type 4 diabetes. For example, weight loss is a common recommendation for people with type 2 diabetes. This isn’t effective for people with type 4 diabetes. They generally already have moderate weight and increased weight loss doesn’t reduce the number of regulatory T cells.

Right now, studies in mice show that type 4 diabetes appears to be linked to the aging process. More studies in humans need to be done to support this theory. Until we know the results of these studies, we won’t know if there is any way to prevent the condition.

Getting medical care is important no matter what kind of diabetes you have. Talking with a medical professional about your symptoms is often the first step toward diagnosis. If you have a primary care physician, they may be a great place to start, but they might not be your last step. Other great ways to get help include:

  • Contacting an endocrinologist. Endocrinologists are doctors who specialize in hormonal conditions such as diabetes. You can find an endocrinologist in your area using this directory. If you have insurance, your insurance provider might also be able to direct you to a local specialist.
  • Finding a local diabetes education program. Diabetes education programs can help you learn to manage your condition. Educational specialists can help you make a plan and give you the tools you need to live well with diabetes. You can check for programs in your area here.
  • Talking with a dietitian. A dietitian can develop eating plans for you that will help keep your blood sugar under control. They’ll show you how to make food choices that will help you feel better. You can search for local professionals in this guide.
  • Visiting the American Diabetes Association (ADA) website. The ADA has a wealth of resources for people with diabetes, including educational information for people who have just been diagnosed.

Insulin resistance is a hallmark of type 2 diabetes, and is often connected with having obesity. However, Type 4 diabetes shows that this isn’t always the case.

Studies in mice have shown that the aging process can cause the body to produce too many regulatory T cells. These cells can lead to type 4 diabetes.

These results still need to be studied in humans. Finding evidence of this same pattern in humans could lead to increased diagnosis and the development of new treatments for diabetes.