• Posted September 3, 2025

Could Diabetes Drug Metformin Change Metal Levels in Your Blood?

The diabetes drug metformin has been a mystery for more than six decades.

The most prescribed diabetes med in the world, metformin is very effective in lowering blood sugar levels.

But no one knows exactly how it works.

But a new study sheds some light on metformin’s magic, potentially opening the door for development of even better diabetes drugs, researchers report.

At least some of the drug’s benefits appear to be tied to the way it affects blood levels of certain metals like copper, iron and zinc, according to results published Aug. 31 in the journal BMJ Open Diabetes Research & Care.

Specifically, people taking metformin have significantly lower copper and iron levels and higher zinc levels, researchers said.

“It is significant that we could show this in humans,” senior researcher Dr. Wataru Ogawa, an endocrinologist at Kobe University in Japan, said in a news release.

“Furthermore, since decreases in copper and iron concentrations and an increase in zinc concentration are all considered to be associated with improved glucose tolerance and prevention of complications, these changes may indeed be related to metformin’s action,” Ogawa added.

For the study, researchers recruited 200 diabetes patients at Kobe University Hospital. Half took metformin, and half did not.

“It is known that diabetes patients experience changes in the blood levels of metals such as copper, iron and zinc,” Ogawa said. “In addition, chemical studies found that metformin has the ability to bind certain metals, such as copper, and recent studies showed that it is this binding ability that might be responsible for some of the drug’s beneficial effects.”

Blood tests showed that metformin did indeed alter patients’ levels of various metals.

These insights will be used to help judge a new diabetes drug called imeglimin, a derivative of metformin that shouldn’t be able to bind metals in the same way.

“Imeglimin is thought to have a different method of action, and we are already conducting studies to compare the effects the two drugs have,” Ogawa said.

However, Ogawa added that even more research is needed to figure out the way metformin works.

“We need both clinical trials and animal experiments to pinpoint the causal relationship between the drug’s action and its effects,” Ogawa said. “If such studies progress further, they may lead to the development of new drugs for diabetes and its complications by properly adjusting the metal concentrations in the body.”

More information

The Mayo Clinic has more on metformin.

SOURCE: Kobe University, news release, Aug. 31, 2025

What This Means For You

Newer drugs that work better than metformin could be developed if the way it works is figured out.