What Is Type 3 Diabetes?

Many people know about Type 1 and Type 2 diabetes. But maybe you’ve also heard the term “Type 3 diabetes.” It’s not a new kind of diabetes, or a diagnosis you will see in your medical chart. It’s a term that describes the effects of diabetes on the brain. 

Here, we’ll talk about the connection between diabetes and dementia. And how you can lower your risks and optimize the health of both your body and your brain. 

What is Type 3 diabetes?

Most people with diabetes don’t have dementia. But they have a higher risk for it over time. People with Type 2 diabetes have a 40% to 60% greater chance of Alzheimer’s dementia. And the risk of vascular dementia is around 90% higher for people with Type 2 diabetes compared to people without diabetes.

In Type 2 diabetes, the cells in the body don’t use insulin effectively. That can lead to organ damage over time. Recent research shows that the same thing can happen to brain cells. Brain cells that have trouble using insulin don’t work as well as they should. That can result in problems with thinking and memory. Type 3 diabetes is a way to talk about the brain changes that happen for some people with Type 2 diabetes. 

Is Type 3 diabetes different from Alzheimer’s disease?

Type 3 diabetes isn’t the same thing as Alzheimer’s disease. But there’s still a connection between the two conditions.

Alzheimer’s disease is the most common cause of dementia. The biggest risk factor for Alzheimer’s is older age. But diabetes is a risk factor as well. 

There’s more to learn about the exact ways that diabetes affects brain cells. But people who have had high blood sugar for longer periods of time have a greater risk of dementia than those whose sugar levels are well managed. People who have more episodes of hypoglycemia, or low blood sugar, also have a higher risk. 

Most studies on diabetes and dementia have looked at people with Type 2 diabetes, which is much more common than Type 1 diabetes. But one large review found that people with Type 1 diabetes may also have a 50% higher risk of dementia as they age. 

For some people, there may be a shared genetic risk for both Type 2 diabetes and Alzheimer’s disease. One gene, called APOE4, is a known risk factor for Alzheimer’s disease. It turns out that the same gene may affect how the brain uses insulin. 

People with Alzheimer’s disease are also more likely to develop Type 2 diabetes. Interestingly, researchers have also noticed that dementia in some people with diabetes progresses more slowly. And it looks a little different on tests like CT scans and MRIs. This subset of people often have more muscle loss and weakness, and may need to use more insulin. Research in this area may help to develop new kinds of treatment.

How is Type 3 diabetes different from other types of diabetes?

There are four main types of diabetes:

• Type 1 diabetes happens more often in children and young adults. It’s an autoimmune condition that damages the cells in the pancreas that make insulin. People with Type 1 diabetes have to use insulin every day. 

• Type 2 diabetes is more common in adults. The body’s cells don’t use insulin well, which leads to higher blood sugar. Type 2 diabetes is treated with diet, exercise, and medications that may or may not include insulin. 

• Gestational diabetes is high blood sugar that happens during pregnancy. Glucose levels may return to normal after pregnancy. But people with gestational diabetes have a higher risk for Type 2 diabetes later on.

• Other types that result from taking certain medications or having other medical conditions. These can sometimes lead to high blood sugar. Of note, diabetes that results from a pancreatic disease is sometimes called “Type 3c” diabetes. This isn’t the same as Type 3 diabetes. 

Type 3 isn’t a diagnosed form of diabetes. It’s a way to think about the insulin resistance and damage to brain cells that occur in some people with diabetes.

Can Type 3 diabetes be prevented or treated?

Yes, there are things you can do to prevent Type 3 diabetes. Caring for your diabetes lowers dementia risk.

Things you can do to lower your risks include:

• Aim for blood sugar levels within the target range: Blood glucose that is too high or too low is risky for brain cells.

• Manage blood pressure and cholesterol: These conditions often go along with Type 2 diabetes. Managing them also supports brain health.

• Eat a balanced and nutritious diet: Eating plans like the MIND diet, DASH diet, and Mediterranean diet all have evidence for both diabetes management and brain health.

• Stay active: Doing regular physical activity helps manage blood glucose and blood pressure. And it improves memory, focus, and mood.

• Ask about medications: If you have diabetes, talk with a healthcare professional about medications that might also support brain health. Some, including GLP-1s like semaglutide (Ozempic), may help lower the risk of dementia. 

• Avoid smoking and heavy alcohol use: Smoking and alcohol both increase the risk for Alzheimer’s disease. 

• Optimize your sleep: Getting at least 7 hours of quality sleep at night helps to protect brain cells.

• Keep your social connections active: People who have limited contact with others may have an increased risk of dementia.

• Get support for stress, anxiety, and depression: Treating depression can lower the risk of Alzheimer’s. And it can also improve symptoms for people who have dementia.

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Written by:

Anne Jacobson, MD, MPH

Anne Jacobson, MD, MPH has been a board-certified physician since 1999. She was a full-scope family physician (inpatient, outpatient, obstetrics, and office procedures) in the Cook County Ambulatory Health Network for 15 years.

Edited by:

Katie E. Golden, MD

Katie E. Golden, MD, is a board-certified emergency medicine physician and a medical editor at GoodRx.

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