Adding Insulin to Metformin May Carry Risk

Diabetes patients taking metformin may have higher death risk after adding insulin than sulfonylureas

/ Author:  / Reviewed by: Joseph V. Madia, MD Beth Bolt, RPh

(RxWiki News) In some cases, lifestyle changes aren’t enough to treat diabetes, and medication is required. There are a variety of diabetes treatment options, but some options may carry more risks than others.

A recent study found that diabetes patients taking metformin had a higher risk of death when insulin was added to their treatment than when sulfonylureas were added to treatment.

"Discuss treatment options for diabetes with your doctor."

This study was led by Christianne L. Roumie, MD, of the Veterans Health Administration–Tennessee Valley Healthcare System Geriatric Research Education Clinical Center in Nashville, TN.

Dr. Roumie and team used data from the national Veterans Health Administration, Medicare and National Death Index databases. The selected databases included information on veterans with type 2 diabetes treated with metformin initially and later with metformin plus insulin or a sulfonylurea (e.g., glipizide, glimepiride, tolazamide) between 2001 and 2008.

Type 2 diabetes is a condition in which the body either doesn’t make enough of the hormone insulin or is unable to use insulin properly, leading to high blood sugar levels. One of the most common treatments for diabetes is metformin, which can be combined with insulin injections or sulfonylureas, a class of medications that can increase the body’s production of natural insulin.

Dr. Roumie and colleagues reviewed data on 178,341 patients being treated for diabetes with metformin alone. Of these patients, 2,948 added insulin to their treatment, while 39,990 added a sulfonylurea medication.

These researchers set out to determine differences in death rates between patients taking metformin and insulin and those taking metformin plus a sulfonylurea. The team looked specifically at deaths caused by heart attack and stroke. All other causes were simply categorized as "all-causes."

The data showed a moderately higher rate of death in the all-cause category among patients who were treated with insulin along with metformin.

The analysis showed no statistical difference in the rate of death from heart attack and stroke between the patients who had added insulin and those who added a sulfonylurea to their metformin regimen.

The authors of this study concluded that there was no advantage to receiving insulin compared to a sulfonylurea medication, and that there was some risk in treating with the combination of metformin plus insulin.

These authors noted that further research is needed to understand the interactions between metformin and insulin.

They also acknowledged that their study was limited by an inability to know the severity of the patients' diabetes or their overall health.

This study was published June 10 in JAMA.

This work was funded by the Agency for Healthcare Research and Quality.

The authors made no disclosures.

Review Date: 
June 10, 2014
Last Updated:
June 11, 2014