Metformin in People With Kidney Disease

Just over one year ago here at Diabetes Flashpoints, we discussed the possibility that hundreds of thousands of people with both diabetes and kidney disease might benefit from taking the diabetes drug metformin. As we noted then, this drug has carried a “black box” warning on its label — mandated by the U.S. Food and Drug Administration (FDA) — ever since it became available in the United States in 1994, due to concerns about lactic acidosis. This rare but extremely serious reaction was found to be an unacceptably common side effect of a drug related to metformin — phenformin — which was pulled from the U.S. market in 1977. Lactic acidosis is much more common in people with impaired kidney function.


Since metformin’s warning label is based, in part, on concerns about a different drug entirely, many researchers have tried to estimate how safe metformin is for people with diabetes whose kidney function is impaired. Last year, we noted that many researchers believe metformin is safe for people with mild to moderate kidney disease, defined as having an estimated glomerular filtration rate (eGFR) of 30–60 ml/min. And one study found that using a safety cutoff of an eGFR of 30 ml/min, nearly one million people in the United States who currently don’t take metformin because of the FDA’s labeling might be able to safely do so.

So what’s changed in the last year? The evidence, it seems, has only grown stronger in favor of metformin being more widely prescribed to people with kidney disease. As noted in a recent article at, the blood-glucose-lowering benefits of loosening restrictions on metformin could be enormous. One study cited in the article, published last August in the journal Diabetes Care, found that depending on how eGFR is calculated, as many as 834,000 people could be newly eligible for metformin if the eligibility threshold were set at an eGFR of 45 ml/min or higher. Notably, this threshold is more conservative than the one in the study we cited a year ago (an eGFR of 30 ml/min) — yet the number of people who could benefit from it, according to the more recent study, is almost as high.

And according to the newer study, if a less cautious threshold of an eGFR of 30 ml/min were to be used for metformin eligibility, as many as 1.63 million people might be able to benefit from the drug. Among different demographic groups, men were more likely than women to become eligible for metformin if kidney-function restrictions were loosened and based on eGFR. Non-Hispanic black people were also more likely than other racial or ethnic groups to stand to benefit from a loosening of restrictions.

What’s your take on the FDA’s “black box” warning on metformin and lactic acidosis — based on what you’ve read or heard, should it be relaxed or changed? If you have chronic kidney disease, have you talked to your doctor about taking metformin? What was the outcome of your discussion? Do you know of any doctors who have prescribed metformin to people with chronic kidney disease despite the FDA’s warning? Leave a comment below!

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  • The question to ask are the guidelines clear for Metformin Drug Administration in medically underserved cities like Chicago, Boston, and New York? And, I got one question in terms of USMLEs step 1 about Metformin Drug Administration in the Internal Medicine section. Now in terms of endocrinology, AMA says don’t prescribe Metformin Drug Administration, but use alternative clinical strategies?

  • Peggy Makepeace

    I am 74 year old female. Been taking metformin for 23 years. It is so good for the heart, but I do have kidney
    disease. My primary care doctor is a kidney doctor. He says I will never have to be on dialysis. He has no problem with metformin.

  • C.P.

    I am 81 years old with diabetes for the past 20 years. Being
    involved in the development of “glucose measuring devices”, I have gone through
    several personal trials with drugs to treat hyperglycemia. Because I understand
    the efficacy of drugs in relation to glucose measurements, I observed that most
    important criteria to monitor the progression of diabetes is to measure “post
    prandial glucose”, (PPG) in place of
    morning fasting readings. When I added Metformin doses in increments to my regimen
    of oral medicines and SQ insulin, the occurrence of high PPG quickly subsided
    and the up swings reappeared when I returned to decreasing doses of Metformin. I
    am aware that Metformin is not prescribed solely to control PPG. In relations
    to kidney functions, my CRCL is just above 60; hence I still have a room to add
    more of Metformin to present cycle of 500 mg twice a day if needed. Lactic
    acidosis, I have not seen with any of my diabetic patients.

  • HV

    No, no, no! Metformin almost destroyed my kidneys a few years ago. I will never take it again no matter how many “experts” come up with the suggestion. It’s being pushed on us by the drug companies!

    • val rab

      I’ve been using Metformin for years and have not problem with my kidneys according to lab results.

  • BK former CDE

    Metformin has so much going for it. I can understand why one’s personal experience would influence their opinion, but it if effective, it does not promote weight gain, it has other benefits as well and it is cheap. I’d be more afraid that drug companies will not want to produce it because there isn’t much to be made except that the large numbers who need it probably keep a comfortable profit margin. Drug companies want the bigger bucks. It is definitely not them making the recommendation for it being the first line of therapy for type 2 after lifestyle changes in people with no contraindications.

  • rem

    I have type 2 diabetes and i m using metformin 1000mg . i have problem to kidney stone also may i take metformin???

  • Roseanne01

    I’ve been taking metformin for thirty years. Have CKD (egfr of 30) because of the blood pressure drug enalipril. Despite how long I’ve had type 2 I gave no peripheral neuropathy and no eye disease. That’s what clued my new endcrinoligist and GP into it being that medication. Not that you can generalise that, but with less stress and a new medication regime I feel better than I have in years. I’m very wary of any medical research coming out of the US as big pharma is very profit motivated. I tend to check what’s being said in UK and Australia where a huge percentage of health care and research us government funded, and where there is global access to medications cheaply, and it’s well controlled. I’ve had no lactic acidosis over all those years and I was on huge doses of metformin (up to 3000mg) though much less now. I think it’s important to stay informed, but to stay cynical. As with Enalipril a lot of the side effects are hidden or not reported.

  • Roseanne01

    Get a second opinion if you can. High blood sugar damages kifpdneys as does high blood pressure (stress?)

  • Jeri

    My husband was on metformin for 14 years and his blood sugars were very well controlled. His gfr dropped to 49 and his doctor took him off of it. Since then we have been fighting high sugars and he has to take both kinds of insulin all day. I’m hoping she will put him back on metformin.

  • Gary Feierbach

    metformin is being touted as an anti-aging drug candidate since it is known to kill senescent cells and has increased the longevity of small mammals. The puzzling thing is the copying over the the contraindications from phenformin to metformin without evidence. That’s caution without evidence with the potential to shorten the lifetimes of a million or more people.

  • Carrie Tuttle

    My gfr is usually 33–38. The doctor wants me off Metaforum and on glipizide. I compromise. I take a glipizide am. and Metaforum pm. I do better and trust Metaforum more.

  • Deb

    I also was born with one kidney I just found out in November 2017
    I recently had surgery on my kidney to remove a cancerous growth and then ended up having another surgery for a blocked bowel with scar tissue also the top and bottom of my bowel was folded over
    My doctor wants me off metformin She says it is not good on my kidney and can cause further damage
    I noticed your post is a couple years old. I hope you are doing well
    Oh my cancer is gone and hopefully it will not come back I have had two other cases of cancer not involving my kidney

  • GrammieConnine

    I took Metformin for over 20 years. My blood sugar was well controlled, my a1c rarely went over 6. Then my kidney function started dropping. When my eGFR dropped to 33 my doctor and I became concerned. My doctor took me took me off Metformin and onto a once a day insulin injection. Within months my eGRF went up to 45. I will never ever take Metformin again.