Researchers studied whether metformin, a popular diabetes medication, affects how much copper, iron, and zinc stay in your blood. They compared 93 people taking metformin with 96 people not taking it. They found that people on metformin had lower levels of copper and iron in their blood, but higher levels of zinc. While these changes are interesting, scientists aren’t yet sure if they help or hurt patients. This discovery might explain some of the unexpected health benefits people have noticed from taking metformin beyond just controlling blood sugar.

The Quick Take

  • What they studied: Does metformin, a common diabetes medicine, change the levels of metals like copper, iron, and zinc in people’s blood?
  • Who participated: 189 adults with type 2 diabetes: 93 people who had been taking metformin for at least 6 months and 96 people who weren’t taking it
  • Key finding: People taking metformin had noticeably lower copper levels (16.0 compared to 17.8 units) and lower iron levels, but higher zinc levels. These differences were statistically significant, meaning they’re unlikely to be due to chance.
  • What it means for you: If you take metformin, your body may be processing metals differently than someone not on the medication. This could potentially explain some of metformin’s health benefits, but more research is needed to understand if these changes are actually helpful or harmful.

The Research Details

This was a cross-sectional study, which is like taking a snapshot in time. Researchers recruited two groups of people with type 2 diabetes—one group taking metformin and one group not taking it—and measured their blood metal levels once. They didn’t follow people over time or randomly assign them to take metformin; instead, they compared groups that already existed. This type of study is useful for spotting patterns and differences between groups, but it can’t prove that metformin directly causes the metal changes because other factors might be involved.

The researchers measured copper, iron, and zinc levels in everyone’s blood. They also looked at related measurements like how much iron was being stored in the body and vitamin B12 levels. They used statistical methods to check whether metformin use was truly connected to these metal changes, even after accounting for other things that might affect metal levels (like age, diet, or other medications).

Understanding how metformin affects metals in your body is important because metformin is one of the most widely prescribed diabetes medications worldwide. Scientists have known for years that metformin can grab onto metals in test tubes, but they didn’t know if this actually happened in real human bodies. If metformin really does change metal levels, it might explain why the drug seems to help with inflammation and possibly even cancer risk—effects that go beyond just lowering blood sugar.

This study has some strengths: it measured metal levels carefully in a decent-sized group of people, and the researchers used proper statistical methods to check their findings. However, there are important limitations. Because it’s a snapshot study rather than following people over time, we can’t be completely sure metformin caused the changes—other lifestyle differences between the groups might explain the results. The study was also relatively small, so the findings need to be confirmed in larger groups of people.

What the Results Show

The main finding was that people taking metformin had significantly lower copper levels in their blood compared to those not taking the drug (16.0 versus 17.8 micromoles per liter). This difference was statistically significant, meaning it’s very unlikely to have happened by chance. When researchers used advanced statistical methods to account for other factors that might affect copper levels—like age, body weight, kidney function, and other medications—metformin use remained strongly connected to lower copper.

Beyond copper, the study found that metformin users also had lower iron levels in their blood (about 2.5 units lower on average). Again, this difference held up even after accounting for other factors. Interestingly, the pattern was opposite for zinc: people taking metformin actually had higher zinc levels than those not taking it. These weren’t tiny differences—they were large enough that the researchers felt confident they were real and not just random variation.

The researchers also looked at vitamin B12 levels because metformin is known to sometimes interfere with B12 absorption. They found that metformin users had significantly lower B12 levels (338.7 versus 412.8 picomoles per liter). This finding aligns with what doctors already know—some people on metformin need to take B12 supplements. The study also measured iron-related markers like ferritin (a protein that stores iron), and these showed similar patterns to the iron levels themselves, suggesting the changes were consistent across related measurements.

Scientists have known for decades that metformin can bind to metals in laboratory settings, but this is one of the first studies to show it actually happens in living people. Previous research suggested metformin might have anti-inflammatory and anti-cancer effects that couldn’t be fully explained by blood sugar control alone. This study provides a potential mechanism—by changing metal levels, metformin might be triggering these additional benefits. However, most research on metformin’s benefits has focused on blood sugar control, so this metal-dynamics angle is relatively new territory.

The biggest limitation is that this study is a snapshot, not a long-term follow-up. We can see that metformin users have different metal levels, but we can’t prove metformin caused these differences—other lifestyle factors between the groups might explain it. The study was also relatively small (189 people), so results need confirmation in larger populations. Additionally, the study didn’t measure how long people had been on metformin or their exact doses, which could affect the results. The researchers also couldn’t determine whether these metal changes are actually beneficial, harmful, or neutral for patients’ health. Finally, the study included only people with type 2 diabetes, so we don’t know if these findings apply to people without diabetes.

The Bottom Line

If you take metformin, there’s no need to change anything based on this single study. However, this research suggests it might be worth discussing with your doctor whether you should have your B12 levels checked periodically, since the study confirms metformin can lower B12. Some doctors already recommend this. Don’t stop taking metformin or change your dose without talking to your doctor—the benefits of metformin for blood sugar control are well-established and important. More research is needed before we know if the metal changes are helpful or harmful.

This research is most relevant to people with type 2 diabetes who take or are considering metformin. It’s also interesting to doctors and researchers studying how metformin works. If you have concerns about metal levels or B12 deficiency, discuss this with your healthcare provider. People without diabetes don’t need to worry about this research affecting them.

If metformin does change metal levels, the changes likely develop gradually over weeks to months of taking the medication. This study measured people who had been on metformin for at least 6 months, so that’s probably the timeframe needed to see these changes. You wouldn’t expect to notice any symptoms from these metal changes in the short term, though B12 deficiency can cause fatigue or nerve problems if it becomes severe over time.

Want to Apply This Research?

  • If you use a health tracking app and take metformin, consider logging your B12 supplementation and any symptoms of B12 deficiency (like unusual tiredness or tingling in your hands/feet). Track when you have blood work done and note your B12 levels if available.
  • Set a reminder to discuss B12 screening with your doctor at your next appointment if you’ve been on metformin for 6+ months and haven’t had recent B12 testing. If your doctor recommends B12 supplementation, use your app to track whether you’re taking it consistently.
  • Create a long-term tracking system in your app to monitor: (1) dates of B12 blood tests and results, (2) any B12 supplements you take, (3) symptoms that might indicate B12 deficiency (fatigue, numbness), and (4) your metformin dose changes. Share this information with your healthcare provider at regular check-ups.

This research is preliminary and describes associations observed in one study, not proven cause-and-effect relationships. The findings do not suggest any changes to metformin treatment. If you take metformin, continue taking it as prescribed by your doctor unless directed otherwise. Discuss any concerns about metal levels, B12 deficiency, or medication side effects with your healthcare provider. This information is educational and should not replace professional medical advice. Always consult with your doctor before making changes to your diabetes management or supplementation.