Double trouble? A look at double diabetes

By Credentialled Diabetes Educator, Carolien Koreneff

Double diabetes

Double diabetes is a term unofficially used to describe people who live with type 1 diabetes, but who also have insulin resistance, the main feature of type 2 diabetes. How much insulin resistance is present can vary from one person to the next.

To explain this in more detail it’s helpful to first revisit the difference between type 1 and type 2 diabetes.

Type 1 diabetes

Type 1 diabetes is usually an auto-immune condition in which the immune system mistakenly attacks the insulin-producing cells in the pancreas. As a result, the body produces little or no insulin. People with type 1 diabetes need daily insulin injections or an insulin pump to manage their condition.

Type 2 diabetes

People with type 2 diabetes generally produce insulin, but this insulin does not work well. This is called insulin resistance. The pancreas compensates by making more insulin but not enough to lower the glucose to normal levels. People with type 2 diabetes are often prescribed tablets to help address the insulin resistance. However, over time the pancreas may start to wear out and this can lead to what is known as insulin deficiency. Insulin injections may then become necessary. This does not mean that the person now has type 1 diabetes; they still have type 2 diabetes, but are now insulin requiring.

Mixed diabetes and double diabetes

Mixed diabetes and double diabetes are essentially the same thing. They both refer to a condition where someone has characteristics of both type 1 and type 2 diabetes. This often occurs when someone with type 1 diabetes develops insulin resistance, this may be associated with weight gain.

The term double diabetes was first coined in 1991, when researchers noticed that people with type 1 diabetes and a family history of type 2 were more likely to become overweight and require higher doses of insulin. Some of these individuals might have developed type 2 diabetes later in life had they not first developed type 1.

There have also been some instances where a person thought to have type 2 diabetes were subsequently found to have evidence of auto-immune, type 1, diabetes. This would typically be classified as Latent Auto-immune Diabetes in Adults (LADA).

Double or mixed diabetes are not official terms and health professionals should not the terms unless brought up be the person living with diabetes.

Characteristics of double diabetes

Double or mixed diabetes can affect individuals of any age, weight or body type. Key features include:

• The presence of autoimmune destruction (type 1) and insulin resistance (type 2).
• Often associated with weight gain or obesity in people with type 1 diabetes, leading to insulin resistance.
• Requires a combination of insulin therapy and treatments for insulin resistance, including lifestyle changes and medications

Insulin resistance in double diabetes

Risk factors for insulin resistance include excess weight, smoking, inactivity, certain medications (like steroids), family history of type 2 diabetes, puberty, and ethnic background. There are some risk factors you can change, and some (like your family history and ethnic background) you cannot.

Managing double diabetes is challenging. Insulin resistance makes blood glucose harder to manage and can increase the risk of heart problems.

Simple lifestyle changes, such as a healthier diet and a regular exercise plan, can often help reverse insulin resistance in people with type 1, type 2, and double diabetes. However, due to the need for insulin injections (and some other factors) managing weight can be challenging despite the person’s best efforts.

People with double diabetes can gain a lot of weight. This leads to needing more insulin, and weight gain from insulin treatment can lead to further insulin resistance, and other health problems. Some people gain weight more easily because of their family history, or because of how their body handles food and insulin. This causes a lot of frustration, as people with double diabetes can struggle to maintain their weight, despite their best efforts.

How common is double diabetes?

Double diabetes is rising globally, especially in children and adolescents. This is due to obesity and lifestyle changes.  

One study found that nearly a quarter of all people with type 1 diabetes showed features of the metabolic syndrome.² In rapidly developing countries, like Saudi Arabia, nearly one-third of young people with diabetes show double diabetes traits.

Treatment of double diabetes

The management of double diabetes focuses on reducing any insulin resistance, while maintaining glucose levels in the target range, as much as possible.

With these goals in mind, treatment includes:

• Insulin to replace any insulin the body no longer produces
• Medications such as Metformin to reduce insulin resistance
• Lifestyle changes, such as healthy eating and regular exercise

Some newer diabetes medications, which can help reduce insulin resistance, are not suitable for people with type 1 diabetes, or are considered off-label prescribing due to safety concerns.

SGLT-2 inhibitors, such as Forxiga, Jardiance, help lower blood glucose, reduce blood pressure, and support weight loss. While these medications are effective in type 2 diabetes, they can significantly increase the risk of diabetic ketoacidosis (DKA) in people with type 1 or double diabetes. DKA is a serious and potentially life-threatening complication, making this a potentially dangerous option for some people with type 1 or double diabetes.

Incretin mimetics, commonly used to treat type 2 diabetes, include GLP-1 receptor agonists such as Ozempic and Trulicity and DPP-4 inhibitors (also known as gliptins). These medications work by enhancing the effects of incretin hormones, which stimulate insulin release, suppress glucagon, and slow digestion.

• GLP-1 receptor agonists are injectable drugs that can help lower glucose levels, promote weight loss, and potentially reduce insulin requirements. However, they may cause side effects such as nausea, vomiting, and diarrhoea. In rare cases, they have been linked to pancreatitis. Because they slow gastric emptying, there’s also a risk of low blood glucose (hypoglycaemia) when used with insulin. Their use in type 1 or double diabetes is considered off-label and should only be pursued with specialist advice.
• DPP-4 inhibitors are oral medications that enhance incretin levels by preventing their breakdown. While not currently approved for type 1 diabetes, they are being investigated for their potential to preserve beta-cell function, improve glucose stability, and reduce inflammation, particularly in people with LADA. They may be used as an add-on to insulin, but never as a replacement, and always under careful supervision. Ongoing monitoring and clear communication with the diabetes care team is essential.

While these newer medications offer promise, more research is needed to determine their safety and long-term effectiveness in people with double diabetes.

Insulin pumps can be a useful tool to limit the amount of insulin injected daily. Reducing the total daily insulin dose can help limit weight gain and insulin resistance When using an insulin pump miniscule amounts of insulin are delivered across the day, mimicking the body’s natural insulin release more closely than injections. The newer closed-loop systems, also known as automated insulin delivery (AID) devices, adjust insulin doses based on results from a continuous glucose monitoring (CGM) sensor. These systems have been shown to improve time in range and reduce overall insulin needs.

Researchers are working on new insulins that target the liver more than other tissues. Early data suggests that this can reduce weight gain and as a result be more useful in people with double diabetes. However, it is early days; more research is needed to understand how to prevent and treat double diabetes.

Double diabetes and complications³

People with double diabetes tend to have an increased risk of high blood pressure, heart disease, stroke and foot problems.

The risk of developing kidney complications and retinopathy (eye damage) is also increased in people with double diabetes, even if the diabetes is well managed.This happens through insulin resistance, weight gain, fat changes, and family history.

Fat can also build up in muscles and organs, including the liver and heart. This raises the likelihood of non-alcoholic fatty liver disease, which can progress to inflammation and scarring of the liver. Non-alcoholic fatty liver disease can worsen diabetes complications and increase the risk of liver-related issues, such as cirrhosis.

Double diabetes presents unique challenges, but understanding the condition is the first step in managing it effectively. With the right support, tailored treatment, and ongoing research, people with double diabetes can improve their outcomes and quality of life.

Maureen’s experience

Although I lost 40kgs before falling pregnant, I had gestational diabetes and after the delivery of my daughter my blood glucose levels remained high. It took my doctor another six years to diagnose diabetes. I was initially told I had type 2 diabetes and was started on tablets, but these did not seem to work. It wasn’t until I presented to hospital with DKA that I was started on insulin (again, I was on insulin during the pregnancy as well). At the hospital I was told I had type 1.5, which I now understand is LADA, but I was also told to continue the oral medication as I have insulin resistance.

When I tell people I have diabetes they immediately think I have type 2 diabetes because I am overweight. Some people even try to tell me that diabetes is reversible. I then have to explain that no, I have type 1 diabetes with insulin resistance, this is not reversible. Even my own doctor does not seem to understand this fully. I am glad my diabetes educator told me I have double diabetes, so I can now explain it better.

Although the issue remains that my levels often go high, despite my best efforts. It seems that the insulin does not kick in until much later. We tried Metformin, but I cannot tolerate it. I follow a low carb diet, do regular exercise, and am now on an insulin pump to help minimise my insulin requirements (this helps the weight a little). I also use CGM to track my levels. I am currently waiting to see my endocrinologist to find out if I can start on some other medication (such as Ozempic) to manage my diabetes and hopefully help me lose weight.

It is very stressful for me to live with double diabetes. I worry about potential complications in the future, relating to high glucose levels, and I have struggled with diabetes burnout a few times these past years. I am very lucky that I have a good educator who supports me through it all.