Metformin is a common medication that helps people manage diabetes by controlling blood sugar. But new research suggests it might do something else too—it could help protect and support your brain. Scientists reviewed 166 studies and found that metformin can cross into the brain and affect how brain chemicals work, potentially helping with memory and protecting against brain diseases like Alzheimer’s. While early results from lab and animal studies look promising, doctors say we need more human studies to be sure it actually works this way in real people.

The Quick Take

  • What they studied: Whether metformin, a diabetes medicine, can affect how the brain works and protect it from damage
  • Who participated: Scientists reviewed 166 different studies—some used animals, some used human cells in labs, and some involved actual patients. The studies came from research databases searched between November 2024 and July 2025
  • Key finding: Metformin appears to reach the brain and may help balance brain chemicals (like serotonin and dopamine) that affect mood, thinking, and memory. It also seems to reduce brain inflammation and protect brain cells from damage
  • What it means for you: If you take metformin for diabetes, it might have extra benefits for your brain health. However, this is still early-stage research mostly from labs and animals—we don’t yet have enough proof that it works this way in humans. Talk to your doctor before making any changes to your medication

The Research Details

This was a systematic review, which means scientists looked at many existing studies and summarized what they found. The researchers followed strict rules (called PRISMA guidelines) to make sure they were fair and thorough. They searched four major scientific databases for studies about metformin and the brain, looking for both animal studies and human research. Two independent reviewers checked each study to make sure it was good quality and relevant to the question.

The researchers looked at 166 studies total. Most were laboratory or animal studies that showed how metformin works in the brain. Some were human studies that looked at whether people taking metformin had better thinking or memory. The team checked each study’s quality to understand how reliable the findings were.

A systematic review is important because it brings together all the available evidence in one place, rather than looking at just one study. This helps us see the big picture and understand what scientists have learned overall. By carefully reviewing 166 studies, the researchers could identify patterns and common findings that might not be obvious from looking at individual studies alone. This type of research is especially useful when we’re trying to understand if a medicine might have new uses beyond what it was originally designed for.

This review followed strict international guidelines (PRISMA 2020) that are designed to make sure systematic reviews are done fairly and thoroughly. The study was registered before it started, which helps prevent bias. However, most of the evidence came from animal studies and lab experiments, not human trials. Animal studies are useful for understanding how something might work, but results don’t always translate to humans. The human studies that were included were small and didn’t all measure the same things, making it harder to draw firm conclusions.

What the Results Show

The research shows that metformin can cross the blood-brain barrier—a protective wall around the brain that normally blocks many substances. Once in the brain, metformin appears to affect several important brain chemicals: serotonin (which affects mood), dopamine (which affects motivation and pleasure), glutamate and GABA (which control how excited or calm brain cells are), acetylcholine (which helps with memory), and norepinephrine (which affects attention).

The studies suggest metformin helps balance these chemicals, which is important because when they’re out of balance, it can lead to problems with thinking, mood, and memory. The research also shows that metformin may reduce inflammation in the brain and help brain cells produce energy more efficiently. These effects appeared in studies of brain diseases like Alzheimer’s and Parkinson’s.

Most of this evidence comes from animal studies and lab experiments where scientists could carefully control conditions and measure specific effects. These studies consistently showed protective effects, meaning metformin seemed to help prevent or slow brain cell damage. However, the human studies were fewer in number and smaller in size, so the evidence is less certain for people.

Beyond the main findings, the research suggests metformin might help with stroke recovery and a genetic condition called fragile X syndrome. Some studies also hinted that people taking metformin might have better cognitive function (thinking and memory skills), though these findings were not as strong or consistent as the brain protection findings. The research also noted that metformin’s benefits appear to come from multiple pathways—it’s not just one mechanism, but several ways it helps the brain work better.

This research builds on earlier observations that metformin might have effects beyond controlling blood sugar. Previous studies had suggested metformin might be neuroprotective, but this systematic review is one of the most comprehensive looks at how it actually works in the brain. The findings fit with what scientists know about how brain diseases develop—they often involve inflammation, energy problems in cells, and imbalanced brain chemicals. Metformin appears to address all three of these issues, which is why it’s generating interest as a potential treatment.

The biggest limitation is that most evidence comes from animal studies and lab experiments, not human trials. What works in a mouse brain or in a dish doesn’t always work the same way in human brains. The human studies that do exist are small and measured different things, making it hard to compare them. We also don’t know the best dose of metformin for brain benefits, or which people would benefit most. The review couldn’t tell us how long it takes to see benefits or how long they last. Finally, most studies were short-term, so we don’t know if metformin’s brain effects continue over years of use.

The Bottom Line

Based on current evidence, we cannot yet recommend metformin specifically for brain health in people without diabetes. If you already take metformin for diabetes, the research suggests it might have additional brain-protective benefits, but this is not proven in humans yet. If you’re interested in this research, discuss it with your doctor—don’t start or stop any medication based on this review alone. Researchers strongly recommend that more human studies be done before making any new treatment recommendations. If you do take metformin long-term, your doctor should monitor your vitamin B12 levels, as metformin can affect how your body absorbs this important nutrient.

People with type 2 diabetes who already take metformin should know about this research, as it suggests their medication might have additional benefits beyond blood sugar control. People with a family history of Alzheimer’s or Parkinson’s disease might find this interesting, but should not start metformin without talking to their doctor first. Researchers and doctors should care about this because it opens new possibilities for treating brain diseases. People should NOT start taking metformin just for brain health based on this review—the evidence isn’t strong enough yet, and metformin is a prescription medication with potential side effects.

If metformin does help the brain, benefits would likely take weeks to months to appear, not days. The animal studies that showed benefits used metformin for extended periods. However, we simply don’t have enough human data to say how long it would take to see real effects in people, or even if the effects would be noticeable in daily life. This is one reason why more research is needed.

Want to Apply This Research?

  • If you take metformin and want to monitor potential cognitive benefits, track your memory and mental clarity weekly using a simple 1-10 scale. Note any changes in focus, word recall, or mental energy. Also track your mood and energy levels, as these relate to the brain chemicals metformin affects.
  • If you’re interested in brain health while taking metformin, combine it with proven brain-healthy habits: get 7-9 hours of sleep, exercise regularly, eat a Mediterranean-style diet rich in vegetables and fish, and do mentally stimulating activities. These changes have strong evidence for brain protection and would work alongside any potential metformin benefits.
  • Keep a simple monthly log of cognitive function (memory, focus, mental clarity) and mood. Share this with your doctor at regular checkups. If you take metformin long-term, ask your doctor to check your vitamin B12 levels annually, as metformin can reduce B12 absorption, which itself affects brain function and memory.

This research is a systematic review of mostly animal and laboratory studies. While the findings are interesting, they do not yet prove that metformin helps the human brain in the ways described. Do not start, stop, or change any metformin or other medication based on this information. If you take metformin for diabetes, continue taking it as prescribed by your doctor. If you’re interested in using metformin for brain health, speak with your healthcare provider first—metformin is a prescription medication with potential side effects and interactions. This summary is for educational purposes only and should not replace professional medical advice. Anyone with concerns about brain health, memory, or neurological conditions should consult with a qualified healthcare provider.