Korin Miller is a health and lifestyle journalist who has been published in The Washington Post, Prevention, SELF, Women's Health, The Bump, and Yahoo, among other outlets.
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For patients with type 1 diabetes who take high doses of insulin, a new study has shed some light on the possible link between insulin use and cancer.
“Both type 1 and type 2 diabetes patients have increased cancer risk,” study co-author Yuanjie Mao, MD, PhD, assistant clinical professor of endocrinology at Ohio University, told Verywell. “But the factors for this increased risk were unknown.”
Because, according to Mao, there are very few clinical studies on type 1 diabetes, his team hoped to explore why the research that does exist links the condition to cancer.
Type 1 diabetes is an autoimmune disease where the pancreas does not make enough—or any—of the hormone (insulin) that lets blood sugar (glucose) enter the cells in the body to be used for energy.
About 5% to 10% of patients with diabetes have type 1 diabetes.
The study, which was published in JAMA Oncology, looked at data from more than 1,300 patients with type 1 diabetes. The researchers grouped the patients by how much insulin they took daily:
The patients were followed by the researchers for almost 30 years. At the end of the study, the researchers noted that the rates of cancer were:
The researchers also found that insulin dose was more strongly linked to a person’s cancer risk than other factors, including their age. Women in the study seemed to have a higher cancer risk than the men.
Mao said that it would be difficult to definitively say that insulin use causes cancer in type 1 diabetes patients.
“Our study did not compare people using insulin versus those not using insulin,” said Mao. “Our study also did not compare the types of insulins or cancers. Our study only suggests a very high dose of insulin use might increase cancer risk.”
The study also had limitations—for one, it was relatively small, and the results did not show that taking insulin was what caused cancer in some of the patients.
The new study did not explore why there is a link between insulin dosing and cancer risk—it just showed that there appears to be one.
That said, Mao offered a few theories about why there could be a link between cancer risk and insulin.
Needing higher levels of insulin could be a marker of insulin resistance (when the body’s cells do not respond well to insulin) that’s being caused by something else. Thus, Mao said that “the link between insulin dose and cancer might be indirect.”
“In our study, we tried to demonstrate the link is directly associated,” said Mao. “Therefore, we included as many potential [cancer] risk factors as possible such as smoking, alcohol use, exercise, diabetes control, and blood pressure control. After adjustments of these factors, the correlation between cancer risk and insulin dose persists.”
A 2016 study found that type 1 diabetes patients had a higher risk of developing some cancers than people in the general population. For example, they were more at risk for stomach, liver, pancreatic, and kidney cancers.
Laurie A. Kane, MD, an endocrinologist at Providence Saint John’s Health Center, told Verywell that if people with type 1 diabetes are worried about the possibility of a link between insulin and cancer, that’s a conversation best had with their provider.
“It’s important that each individual patient focus on measures you can take to lower your insulin and insulin sensitivity,” said Kane.
When it comes to the risk of cancer for women with type 1 diabetes, the findings from Mao’s study lined up with previous research that had also shown a higher cancer risk among women with type 1 diabetes who took insulin. It also showed that the risk is still there regardless of their age or insulin dose.
However, Mao said that the “association is much weaker than insulin dose” and that it remains unclear why there is a gender difference.
For all patients with type 1 diabetes who takes very high doses of insulin, Mao said that “any means of improving insulin resistance, such as weight loss and exercise, can reduce the daily insulin requirement, and might possibly reduce the future cancer risk.”
However, Mao said that because the link between insulin and cancer is complex, more research is needed before any changes to cancer screening would be made.
If you have type 1 diabetes and take high doses of insulin daily and you’re concerned about your cancer risk, talk to your provider. There are many ways that you can work on lowering your risk for cancer as well as complications from diabetes.
Centers for Disease Control and Prevention. What is type 1 diabetes?.
Centers for Disease Control and Prevention. Diabetes fast facts.
Zhong W, Mao Y. Daily insulin dose and cancer risk among patients with type 1 diabetes. JAMA Oncol. Published online July 28, 2022. doi:10.1001/jamaoncol.2022.2960
Carstensen B, Read SH, Friis S, et al. Cancer incidence in persons with type 1 diabetes: a five-country study of 9,000 cancers in type 1 diabetic individuals. Diabetologia. 2016;59(5):980-988. doi:10.1007/s00125-016-3884-9
Korin Miller is a health and lifestyle journalist who has been published in The Washington Post, Prevention, SELF, Women’s Health, The Bump, and Yahoo, among other outlets.
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