Millions of people around the world live with type 2 diabetes and rely on medications every day to keep their blood sugar under control. Managing blood sugar is extremely important because diabetes can damage many parts of the body over time.
However, new research suggests that some commonly used diabetes medications may carry unexpected risks for the heart.
A study led by scientists at Northwestern University has found that two widely used diabetes treatments—sulfonylureas and basal insulin—may increase the risk of serious heart problems. These problems include heart attacks, strokes, and heart failure.
The findings raise important questions about how doctors choose medications for people whose diabetes is not fully controlled by their first treatment.
Type 2 diabetes develops when the body cannot use insulin properly. Insulin is a hormone that helps move sugar from the blood into the body’s cells, where it can be used for energy. When the body becomes resistant to insulin or does not produce enough of it, sugar builds up in the bloodstream.
High blood sugar over a long period can damage blood vessels, nerves, the kidneys, the eyes, and other organs.
Because of these risks, controlling blood sugar is a major goal of diabetes treatment. For most people with type 2 diabetes, doctors first prescribe a medication called metformin. Metformin helps lower blood sugar and improves the body’s ability to use insulin more effectively. It has been used for many years and is generally considered safe and affordable.
However, diabetes often becomes harder to control over time. Many patients eventually need a second medication when metformin alone is no longer enough. For many years, doctors have commonly added drugs such as sulfonylureas or basal insulin at this stage of treatment.
Sulfonylureas are medicines that stimulate the pancreas to release more insulin. This extra insulin helps move sugar out of the blood and into the body’s cells. Basal insulin, also known as long‑acting insulin, is another treatment option. It is designed to keep blood sugar levels steady throughout the day and night.
These medications have been trusted treatments for decades. They are widely used because they are effective at lowering blood sugar and are often less expensive than newer medications. However, the new research suggests that while they help control blood sugar, they may also increase the risk of heart problems.
To better understand these risks, the Northwestern research team studied medical records from more than 132,000 adults with type 2 diabetes. All of the participants had already been taking metformin and needed to start a second diabetes medication.
The researchers compared several types of second‑line drugs to see how they affected heart health in real‑world patients.
This approach is important because many earlier studies were conducted in controlled clinical trials with smaller groups of people. By analyzing health data from a very large population, the scientists were able to see how these medications perform in everyday medical practice.
The results showed clear differences between the medications. People who took sulfonylureas were 36 percent more likely to experience a major cardiovascular event compared with those who used a newer type of drug called DPP‑4 inhibitors. Major cardiovascular events included heart attacks, strokes, and heart failure.
The risk was even higher for people who used basal insulin. According to the study, patients taking basal insulin were about twice as likely to experience these serious heart problems compared with those using DPP‑4 inhibitors.
The researchers also looked at how often these events occurred. They found that among people taking basal insulin, one major cardiovascular event occurred for every 37 patients over a two‑year period. Among people taking sulfonylureas, one event occurred for every 103 patients during the same amount of time.
These numbers may seem small at first, but the impact becomes much larger when considering how many people live with diabetes. In the United States alone, more than 30 million people have type 2 diabetes. Even a modest increase in heart risk could affect a large number of individuals.
Heart disease is already the leading cause of death among people with diabetes. High blood sugar can damage blood vessels and increase the chance of blocked arteries, which can lead to heart attacks and strokes. Because of this, doctors try to choose treatments that help control blood sugar without adding extra risk to the heart.
The study’s lead author, Dr. Matthew O’Brien of Northwestern University, said the findings suggest it may be time to reconsider how doctors treat diabetes after metformin stops working. He explained that medications should not only lower blood sugar but also help protect the heart whenever possible.
In recent years, several newer diabetes drugs have become available. These include GLP‑1 receptor agonists, SGLT‑2 inhibitors, and DPP‑4 inhibitors. Research has shown that some of these newer medications may actually reduce the risk of heart disease in people with diabetes.
However, these newer drugs are often more expensive than older treatments like sulfonylureas and basal insulin. Because of the higher cost, many patients and healthcare systems still rely on older medications that are cheaper and more familiar.
The researchers say this creates a difficult balance between affordability and long‑term health outcomes. While newer medications may cost more at first, preventing heart attacks and strokes could save lives and reduce healthcare costs in the future.
The findings highlight the importance of discussing treatment options with healthcare providers. People living with type 2 diabetes should talk with their doctors about the benefits and risks of different medications. Choosing the right treatment can help manage blood sugar while also protecting long‑term heart health.
The study was led by Dr. Matthew O’Brien and his research team at Northwestern University and was published in the medical journal JAMA Network Open.
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