Long-Term Use of Metformin Does Not Affect Memory, Thinking

Long-term use of the blood-sugar-lowering medicine metformin is not linked with cognitive impairment (problems with thinking, memory, and problem solving), according to new research from Columbia University Medical Center. Metformin is the most commonly prescribed diabetes drug in the world, with approximately 80 million prescriptions for the medicine filled in the United States alone in 2015.


Previous research on metformin, thinking, and memory has had conflicting results, with some studies indicating that the medicine is linked to impaired brain function — perhaps in part due to vitamin B12 deficiency — and even Alzheimer’s disease, and other studies suggesting that it may improve memory.

To further evaluate the association between metformin and cognition, researchers looked at data from more than 2,000 adults enrolled in the Diabetes Prevention Program Outcomes Study. The participants were randomly assigned to either lifestyle intervention (consisting of a diet and exercise plan), metformin, or placebo (inactive treatment) to determine the effects on brain function. In years 8 and 10 of the study, the subjects were given cognitive assessment tests.

The researchers found no significant differences in cognitive performance in participants who had been taking metformin for 8 years compared to those in the lifestyle prevention or placebo groups, and no correlation was found between the length of metformin use and cognitive function. A higher HbA1c level (a measure of glucose control over the previous 2–3 months) at the time of cognitive testing was linked with worse brain function.

The results of the study “should be incredibly reassuring to clinicians and patients who have read reports to the contrary,” noted lead study author José A Luchsinger, MD. “I think that’s enormously important because metformin is the most used diabetes medication in the world, and it’s the one that most people who get diagnosed with Type 2 diabetes get started on.”

The investigators plan to give the participants another round of cognitive testing and also hope to perform brain imaging scans.

For more information, see the article “Long-Term Metformin Use ‘Has No Cognitive Impact’,” or the study’s abstract in the journal Diabetes Care. And to learn more about metformin, read the article “Metformin: The Unauthorized Biography,” by diabetes treatment specialist Wil Dubois.

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    Thank you for this information. Metformin has recently been targeted by the “miracle herbal cures” industry and there is a lot of conflicting information and misinformation being circulated. I personally have no problem with herbals, especially when there is some serious research showing therapeutic value. I’ve used a few and kept with the ones that seemed to work. However I cringe when I see web ads saying things like “Your prescription drug is killing you, stop taking it and use our unproven formula instead”. Many of these are basically a multivitamin with a sprinkling of medicinal sounding herbs added. David Spero occasionally covers some of the supplements that have been shown useful in clinical trials, and that’s great. I would also love to see an article talk about how to separate the hype from the helpful when it comes to vitamins and herbal supplements.

    • Madavor Media

      Hi RAWLCM,

      Thank you for your kind words about this piece — we’re glad you found it useful! And thank you as well for the topic suggestion. We’ve passed it along to Amy Campbell, MS, RD, LDN, CDE, who will be writing up an article on that subject in the coming weeks — stay tuned!


      Diane Fennell
      Senior Digital Editor, Wellness


    Yes Metformin does cause memory loss after long term use. My father started on this medication about 20 years ago and he now has kidney failure and Dementia. We often wondered how did his Dementia come about no one in his family have ever had this association with this illness. After further study and research it was indeed Metformin that caused his dementia. I would advise anyone to use other treatment this is NOT a miracle drug. If your pancreas is functioning properly control your diabetes the correct way with exercise and maintain a good diet. All drugs have side effects so you have to pick and choose your battles. I would advise everyone to seek alternative ways of controlling your illness. I wish someone would have informed me of the long term side effects. No way would I have allowed my father to use this medication.