Metformin and Impaired Thinking


According to new research from Australia, the oral diabetes medicine metformin[1] is linked to impaired brain function, but supplementation with vitamin B12 may reduce some of the cognitive effects. Metformin is the most widely used diabetes drug in the world, with over 61 million prescriptions for the medicine filled in the United States alone in 2012.

To evaluate the effects of the drug on cognitive impairment in people with diabetes, researchers recruited 1,354 people from various locations in Australia. The researchers included people with Alzheimer disease and mild cognitive impairment, as well as those who were cognitively normal, but they did not include people with stroke or neurological conditions other than Alzheimer. The participants had an average age of 73.8 and almost 60% were female

The study used an evaluation known as the mini-mental state exam to determine cognitive performance. According to the results, slightly more than half of the participants were not cognitively impaired, while 21.8% were minimally impaired, 17.7% were mildly impaired, and 10.1% were most impaired.

In their analysis, the researchers found that people with Type 2 diabetes[2] had worse cognitive performance than those without Type 2 and that, among those with diabetes, people taking metformin had worse cognitive performance than those not taking the medicine. Cognitive function scores were also found to be lower among those with vitamin B12 levels of less than 250 pmol/l.

Because metformin is known to be associated with B12 deficiency[3], the investigators suggested that “any effect metformin has on cognitive performance may be at least partially mediated by altering serum vitamin B12 levels.”

Limitations of the study include an insufficient amount of information about the duration of the participants’ metformin use, the severity of their diabetes, or their use of other diabetes medicines, which prevented these factors from being assessed relative to cognitive function.

The researchers suggest that future trials should investigate the link between diabetes, impaired thinking, and metformin, and in the meantime they suggest that physicians monitor the cognitive performance of their patients with diabetes who are using metformin.

For more information, read the article “In Some Patients Metformin Impairs Thinking”[4] or see the study’s abstract[5] in Diabetes Care. And to learn more about metformin and vitamin B12 deficiency, click here.[6]

  1. metformin:
  2. Type 2 diabetes:
  3. known to be associated with B12 deficiency:
  4. “In Some Patients Metformin Impairs Thinking”:
  5. see the study’s abstract:
  6. click here.:

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Diane Fennell: Diane Fennell has been an editor at Diabetes Self-Management magazine since 2003. She is currently the Editorial Director. (Diane Fennell is not a medical professional.)

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