Metformin Affects Hearts of Men and Women Differently

The oral diabetes medicine metformin affects the hearts of men and women differently, according to new research from the Washington University School of Medicine in St. Louis. Metformin is the most widely used diabetes drug in the world, with more than 61 million prescriptions being filled in the United States alone in 2012.


Cardiovascular disease is the leading cause of death in people who have diabetes. To determine whether sex has an effect on the heart’s response to diabetes treatments, researchers randomly assigned 43 women and 35 men with Type 2 to one of three groups: The first group received metformin alone, the second received metformin plus rosiglitazone (brand name Avandia), and the third received metformin plus Lovaza, a type of fish oil prescribed to lower blood fats known as triglycerides.

At the start of the study and at three months in, each participant had a PET scan to evaluate oxygen levels, blood flow, and glucose and fatty acid uptake in the heart; blood tests to measure glucose and free fatty acid levels; and an echocardiogram to evaluate heart function.

Blood glucose levels were well controlled in all three groups. When the groups were compared without separating men and women, no differences were seen in heart metabolism. But when the participants were separated by gender, it became clear that the medicines had different, and sometimes opposite, effects on cardiac function.

The biggest difference between men and women was seen in the group taking metformin alone. The drug appeared to improve heart function in women, but it caused the hearts of men to burn less sugar and more fat — a shift that can eventually cause changes in heart muscle, leading to heart failure.

“Instead of making heart metabolism more normal in men, metformin alone made it worse, looking even more like a diabetic heart. But in women, metformin had the desired effect — lowering fat metabolism and increasing glucose uptake by the heart,” said senior author Robert J. Gropler, MD.

Taking rosiglitazone along with metformin seemed to lessen some of the negative cardiac effects of metformin seen in men. In women, who were already benefiting from the metformin, adding rosiglitazone improved heart function further by reducing the heart’s dependence on burning fat. The addition of Lovaza to metformin did not significantly affect heart function in either direction for men or women.

Although the study was small, Gropler noted, it was quite rigorous in the methods it used to analyze heart metabolism.

The differing reactions of men and women may at least partially explain the conflicting data on some diabetes medicines, since the proportion of men and women in clinical trials may impact whether a drug is found to be safe and effective. As individualized approaches to diabetes therapy become more popular, there should be further investigation into gender-related responses to medicines, the researchers suggest.

Limitations of the study include its small size, as well as an early termination of the rosiglitazone group due to restrictions imposed by the Food and Drug Administration on the use of this medicine (since lifted).

For more information about the research, read the article “Diabetes Drugs Affect Hearts of Men, Women Differently” or see the study’s abstract in the American Journal of Physiology: Heart and Circulatory Physiology.” And to learn more about metformin, click here.

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  • Gary

    So now what? I’ve been taking Metformin (in combination with my low carb diet and exercise program) to improve my insulin sensitivity and to ward off Type II (which two of my siblings and my father have). Am I destroying my heart?


  • Robert Abramson

    It’s always nice to find out that the medical profession,the phamaceutical industry and the FDA are doing their best to put profit ahead of safety. I think the FDA one day will approve a poison that can be prescribed for seniors, so they die before they reach the age where they can collect social security. This could be a platform for the TEA party republicans to save money and lower the national debt.

  • Tim

    Great, I have been a type II diabetic for 15 years and have been on Metformin for all that time. I have also had angioplasty and am on Lantus and Aprida ( pump). Am I excellerating the distruction of my heart? PS my dad died of congestive heart failure (diabetic) and my mom died of a stroke (diabetic) and had a heart attack at age 47. Thoughts? Other althernatives?

  • Mr. Gregg

    Wow!I take Metformin 750 MG and I have long suspected that it did not increase my insulin sensitivity. This report is absolutely amazing! I know that if I ask my specialist, I will be told to stick with the medication and forget this report. Until when? Should I wait until I have contracted heart problems and then I will be told it is common with Diabetics but still stick with Metformin.

    I am stopping my Metformin because I have to worry about one person in this lifetime and it is ME. I do not want to be a statistic.

  • Ed

    Next month another study will contradict this one.
    Have been on Metformin 8 years. Lost 60 lbs.diabetes under control and Exercise daily, walk6-7 miles.
    The people in the study were they overweight did they exercise on a regular basis? Not all the variables are known. I’ll continue to take Metformin
    twice a day until more exact info is known.

  • M. Dodson CMA AAMA

    I am off all forms of Metformin. While on on said medication I constantly suffered from uncontorlable bouts of Diarrhea.

  • Terri

    Any news about Janumet? My doctor put me on that and it scares me to death! Just want to be off all of this medication-period-but that will take soem serious will power and discipline. All of this information is helpful, thanks!

  • Teenie

    I agree, next month/year they will contradict this and some other medicine will be the topic. I was diagnosed with diabetes in 2008 and prescribed Metformin 1000mg. 2X’s a day. Did not have cholesterol problems until shortly after (unless it wasn’t checked). Do you know if taking both Crestor(statin)which is for cholesterol will cause heart problems or will help the heart. Statistics are saying Crestor is bad for you, but the doctor insists on it being taken. Can I get some clarity.

  • brandy

    My doctor had me on metformin to prevent getting diabetes. Is this safe. Should I be worried about taking this?

  • Diane Fennell

    Hi everyone,

    Thank you all for your comments. Just a quick reminder that you should not stop taking metformin — or any medicine — without speaking to your health-care provider first. If you have any questions or concerns about the findings of this study, you should be sure to discuss them with your doctor, who can provide guidance on the best course of action for your situation.

    Diane Fennell
    Web Editor

    • Stephanie

      I’ve been taking metformin for 20years, also found out in 2006 that I have dilated cardiomyopathy and I have a defibrillator implant in 2007, also thyroid cold nodules, I’m afraid that metformin has caused my heath conditions, can I get your opinion??? What should I do?

  • Dan

    I have taken metformin (the ER version gives me diarrhea) since 911. I have also taken glipizide most of the time since then. I had a heart catheter a couple years ago, but the doctor surprised me by saying there’s not much blockage, but I have a weak heart (not a lot of words for the $15k he charged my insurance.)

    p.s. I am reading a book on Obamacare and found out that 50% of the cost will come from Medicare. Since Republicans hate Obamacare so much, it looks like Democrats, especially the President and the House, are more likely to be in favor of the poison drug that was mentioned above by Robert Abramson…

  • Virginia

    I am a retired woman who is a Republican and take Metformin. I do resent Mr. Abramson referral to my political party or the Tea Party advocating death to Anyone!! Where do these dopey liberals get this stuff. Mr Romney has this large family and therefore is not an advocate for abortion and is not a racist,but yet he is accused of being that. I have children and grandchildren and We don’t advocate killing anyone. Good Grief!! If anyone is against people trying to better themselves or getting a job or thinking freely is the miserable liberal 30 somethings who want to be CEO’s the minute they leave college if they make it that far!

    • Miranda Clairice

      Really? You resent this, yet you still have the audacity to refer to liberals as “dopey” and “miserable”? Grow up lady.

  • pat

    Well you hear some kind of news daily??? What in the world?? What now? I exercise mostly every day. I try and watch what i put in my mouth mostly although I am not perfect. I take Kombiglyze XR 2.5 1000 twice a day was on glyburide but I lost weight and was allowed to discontinue taking it. I am asthmatic and have HBP. I am well controlled on all health challenges. I am down about 20 pounds. I am also trusting in God to take me threw……you haave to control this beast some kind of way….I am truly trusting in God to direct my dr and me. that is all I can do.

  • Al P

    How come Janumet wasn’t mentioned? I take 1000 2x’s a day. I have had a heart flutter and they say I now have A-Fib.
    (Which I only get maybe 1 x every couple of months) I’m a 60 year old male and now I’m really worried about my taking Janumet. My last blood test A 1c test was 6.3 do you have any opinion for me. And can you get more information on Janumet. Thanks, Al

  • Trish

    I had been on Janumet…. the only thing I noticed was that I noticed so much hair loss that I stopped taking the meds. I was switched and the hair grew back albeit not as thick. My endocrinologist has tried to ‘make’ me take the Metformin..she even handed me a prescription for it… I handed it back and said never. All the medications out there, there has to be something available other than Januvia and Metformin. Thankfully, I’ve fouund it. It’s your life. Stand up for yourself. You can refuse medication. You can find another doctor. I feel great, my A1C varies between 6 and 7, my morning count is between 70 and 90, and rarely do I take my cover insulin. My bp is good. I will never take Metformin or Januvia… and def. not the Janumet mix. Educate yourself.

  • Ferne

    @Robert Abramson; I think the political statement and remark about poisoning us seniors was uncalled for. We all have our opinions on what is going on but I don’t feel this is the platform. This is medical.

  • Krishna Kumar

    I am taking Metformin for the last 15 years! I am a male, type 2 diabetic with serious heart condition (unconnected with Metformin). So what do I do now? Stop Metformin, which has been the basis of my medications all along? This report needs to be followed by a much larger, carefully controlled study to make me change my medication.

  • ted plottner

    this past I collapsed………it was sudden——–my heart had a 20% fraction—I was in serious—I could not breath——I had been taking Metformin for 3 years and riding a bike and walking and running with no sign of heart or breathing problems???????? what the hell…

  • Dee1956

    Hello, I have been taking Metformin for 6 weeks. It is making me sick. I called the doctor, she said my body would adjust to it in time.
    Yesterday after taking it my heart started to beat oddly. That is it for me. I will control my sugar with diet.
    I looked up adverse reactions to Metformin and found so many side effects on WebMD, I could not believe it.

  • J.Smart

    Taking Metformin as a pre-diabetic, recent elevated glucose due to Lupron (?) Age: 84; Weight 134, 5’8″, not overweight; is 250 mg once a day going to make ANY difference? How can I know – blood tests at intervals of 3 months, seems not too helpful.

  • Mary Cobabe

    My 61 year old son was taking Metformin and it was making him so sick that he quit taking it. I took it years ago & it was before you could look up side effects I did not know that it was causing the diarrhea. I had terrible sudden attacks & had to know where every bathroom was where ever I went. I never knew when I would hit and it was so violent?My life was ruled by it . When I found out it was the Metformin & quit taking it My life got better.No Doctors ever mentioned side effects.Most Doctors push it so that they bully people into taking it. My body never got used to taking it! So Dee you are doing the right thing. J Smart
    You can control “PRE DIABETES ” with diet & Exercise. Do not endanger your health by taking Metformin! Get a different Doctor if you need help.