The People's Perspective on Medicine

Metformin Side Effects | Diarrhea and Other Serious Adverse Reactions

Metformin is the most prescribed drug for type 2 diabetes. It may help against cancers. But metformin side effects are daunting. Some are life threatening.
Metformin prescription pills with identification numbers on blue background ,image of a

Metformin (Glucophage) is a great drug. It is the most popular medicine for treating type 2 diabetes. At last count nearly 17 million Americans take metformin daily. That’s impressive for a drug that that has been on the market in the U.S. since 1995. It was first sold in France in 1957. That’s over 60 years! It is prescribed off-label for polycystic ovary syndrome (PCOS). There is even evidence that this drug may provide benefits against breast and prostate cancer. But metformin side effects can be daunting. However, there is a dark side to metformin that all patients need to be aware of. For one thing, this drug can be hard on the digestive tract, as this reader reports.

Metformin Side Effects and the GI Tract:

Q. I have been on metformin for about three weeks for prediabetes and polycystic ovary syndrome (PCOS). I started with 500 mg and I am supposed to ramp up to taking it three times a day, half an hour before each meal.

I don’t know if I can manage that. Right now I am experiencing stomach upset, nausea and diarrhea. It is hard to take. The doctor says this effect will go away. Is that true?

A. Diarrhea and nausea are very common metformin side effects when people first start taking the drug. Some researchers put the likelihood of diarrhea as high as 30 percent (Medical Hypotheses, Sept. 2017). Many people do find that the initial digestive distress diminishes with time. In contrast, others discover that the side effects continue, and they can’t tolerate the drug. If your discomfort persists, please let your doctor know ASAP!

Many health professionals don’t realize that nausea, stomach cramps and severe diarrhea can occur long after metformin has been seemingly well tolerated. A case report published in the journal Pharmacotherapy (Nov. 2001) was titled Metformin as a cause of late-onset chronic diarrhea.” It concluded:

“Patients with type 2 diabetes who are taking metformin and experience diarrhea deserve a drug-free interval before undergoing expensive and uncomfortable diagnostic tests, even when the dosage has been stable over a long period.”

You can learn more about the history of metformin and some common adverse reactions at this link

Readers Share Other Metformin Side Effects:

More GI Complications:

Debbie in New Mexico also had serious diarrhea!

“I took metformin for years, but then I started to have severe diarrhea. At first I did not know what was causing it. I was having a lot of accidents. It got so bad I could not leave the house.

“My doctor ordered a colonoscopy. All was fine, but I still had severe diarrhea. My doctor felt it was the metformin and took me off of it. He prescribed something else and informed me that it would take a while for the metformin to get out of my system. If it was the metformin, then the diarrhea would eventually go away.

“He was absolutely correct. After three months I no longer am having an issue. So nice to get my life back.”

Vivian in California overcame her metformin side effects:

“I have been on metformin for 12 years. I was on 1000 mgs twice a day but realized it was causing me so much bloating and burping. Now I take only 1000 mgs with my evening meal. My bloating and burping are almost non existent.”

O. in Georgia is still having GI trouble:

“When my hemoglobin A1C went up to 6.2 I was prescribed metformin. After three months on a 500 mg pill three times per day, my A1C dropped to 5.9. My doctor checked my kidney function and then reduced the dose to 500 mg twice per day. 

“At first I was nauseated and had stomach cramps. They gradually subsided. Then I started having really bad diarrhea. After the diarrhea came the heart burn. That was the worst of the metformin side effects.

“I would like to stop taking this medication so I can feel like myself again. I like the fact that it seems to be helpful against a number of different cancers, though. Cancer runs rampant in my family. Nothing helps the horrible heartburn.”

Probiotics for Metformin Side Effects?

We have seen no scientific research to support the benefits of probiotics to counteract the metformin side effects. Nevertheless, some readers report success. 

Cheryl in Illinois shares her experience with probiotics:

“I have been on metformin for about six years. For most of that time I had all the classic stomach problems that goes along with this drug. Diarrhea and stomach cramps were a regular problem.

“One day I saw a comment someone posted about taking probiotics for this problem. I bought the cheapest brand I could find and started taking one per day. I have not had any stomach problems or diarrhea since.”

Larry in New York got some relief with probiotics:

“I too have GI problems with metformin. At first I tolerated 500 mg two times a day for four years. No problems. Then my doctor raised the dose to 1000 mg twice a day. That’s when the diarrhea and gas began.

“My doctor told me to take Metamucil fiber wafers to boost my fiber intake. They were supposed to help absorb extra water in my digestive tract. That helped, but was not perfect. On my own I began taking probiotics. This seems to mitigate the symptoms somewhat, but not 100%.”

Digestive Enzymes for Metformin Side Effects?

Stephan in Wheeling, WV found that digestive enzymes helped him:

“I was able to take metformin for a few years before problems developed. Then I had to go to the bathroom four to five times a day. I lost 40 pounds. I discovered that I needed digestive enzymes (lipase, protease and amylase). It was like flipping a switch. My digestive issues went away almost with the first dose. I have gained weight but not too much. I only have to go to the bathroom once a day.”

David found an extended-release formulation ended his metformin side effects:

“I also had gastrointestinal problems with metformin until I switched to the extended-release formula. Now I have no symptoms at all. With metformin, diet, and exercise, my A1C numbers have been kept in the normal range (4.4 – 6.4%) for several years. I would recommend asking your doctor about the extended-release formula before giving up on metformin. It is available as a generic.”

Switching from generic metformin to brand name Glucophage:

Jim in New York discovered that the generic formulation was a problem:

“I have been taking metformin since 2010. The side effects were bad for a while, but in relying on research from the Peoples Pharmacy and other sources, I found my main problem was generic metformin.

“My uncle, who is a Swiss doctor, told me to never use generics. Now that I am on the real Glucophage, almost all of the side effects are gone. My A1C numbers have dropped. Drugs affect people differently.”

Susan in Cleveland has a similar story:

“Jim, I had the same experience as you did. Metformin made me terribly nauseated, so I did some research.  It suggested brand name Glucophage might not cause that side effect. Long story short; after arguing back and forth with my PCP who stated there was no difference between metformin and Glucophage, he finally agreed to prescribe Glucophage. I’ve been on it for two months, and I’ve had no adverse side effects. My A1C dropped from 8.7 to 6.8 in these two months, and I feel so much better.”

CoEnzyme Q10 vs. Metformin Side Effects:

Elizabeth in Australia came up with something different to counteract metformin side effects:

“I experienced severe diarrhoea when on metformin. At my request, my doctor switched me to the extended-release tablets and I no longer have diarrhoea.

“Many people have reported muscle pain, fatigue and memory loss as a side effect of metformin. A number of prescription medications rob the body of CoQ10, and metformin is one of them. Low levels of CoQ10 cause muscle pain, fatigue and memory loss. Consider taking CoQ10 capsules.”

We must admit that Elizabeth caught us by surprise. We knew that statins can deplete the body of CoQ10. This nutrient is essential for the energy-producing mitochondria in our cells. When we checked Dr. Tieraona Low Dog’s excellent book, Fortify Your Life: Your Guide to Vitamins, Minerals and More, we discovered that metformin may also affect CoQ10. 

Metformin and Kidney Function:

People with kidney disease must have regular blood tests if they take metformin. That is because metformin can make this serious situation worse if the doctor doesn’t monitor kidney function carefully (Oncotarget, Jan. 12, 2018). 

Ralph in Chicago, IL, had a close call:

“I have type 2 diabetes and have taken metformin for six years. I was just released from the hospital after suffering from acute renal failure. My creatinine levels were at 5.7. I was taken off metformin and my numbers have come down. My blood, liver, and kidney functions were tested every 3 months. All were OK, then my kidneys began to fail in a very short time.”

Richard in Dallas describes a similar situation in his wife:

“Metformin can also cause kidney failure. My late wife was taking metformin for several years when her doctor upped her dosage. About three months later she was in the hospital for kidney failure. After two dialyses her kidneys returned to normal. Her kidney doctor said the cause of her kidney failure was metformin, and she could never take it again.”

Lactic Acidosis Can Be a Life-Threatening Metformin Side Effect:

The FDA has a black box warning about metformin side effects.

In it there is a discussion of lactic acidosis:

“Postmarketing cases of metformin-associated lactic acidosis have resulted in death, hypothermia [lowered body temperature], hypotension [low blood pressure], and resistant bradyarrhythmias [irregular heart rhythms]. The onset of metformin-associated lactic acidosis is often subtle, accompanied only by nonspecific symptoms such as malaise, myalgias [muscle pains], respiratory distress, somnolence [sleepiness], and abdominal pain. Metformin-associated lactic acidosis was characterized by elevated blood lactate levels…”

The FDA goes on to say that if lactic acidosis is suspected, metformin must be discontinued immediately and the patient should be treated in a hospital. This is a medical emergency! Other symptoms to be alert for include exhaustion, confusion, weakness, muscle cramps, diarrhea, headache, loss of appetite, stomach discomfort or difficulty breathing.

Greg in Wisconsin shared this story:

“Metformin worked well for me, for about 10 years. It always caused me some stomach discomfort and flatulence. In November, 2016 I ended up in the hospital with severe vertigo. Test results revealed high levels of lactic acid. My doctor suspected lactic acidosis and took me off the drug.”

Dr. J. D. A. in Springfield, MO, offers this overview:

“The elderly are usually a special group. In the case of metformin, the life-threatening adverse reaction of lactic acidosis occurs almost exclusively in excessive doses and with declining kidney function. Most of the diabetes experts I queried 10 years ago did not have any patients over 70 on metformin. Yearly kidney function testing is likely to be inadequate to protect people over 70, those with intercurrent illnesses and with the addition of any new chronic and some short term medications. People with diabetes over 70 are, in my experience, fairly likely to suffer declines in their renal function.”

How Does Metformin Lower Blood Sugar?

Metformin works in part by decreasing insulin resistance. That may be why it can help PCOS. This hormonal condition is associated with too much insulin, insulin resistance and chronic inflammation.

Despite all the metformin side effects mentioned above and other listed at this link, we think this is a very valuable drug. If it turns out to help against various cancers including prostate and breast cancer, then it may become even more popular. Consequently, it is crucial to learn about both the benefits and the risks of this fascinating compound.

You can learn more about the pros and cons of metformin along with other options for controlling blood sugar in our Guide to Managing Diabetes

Share your own metformin story in the comment section below.

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About the Author
Joe Graedon is a pharmacologist who has dedicated his career to making drug information understandable to consumers. His best-selling book, The People’s Pharmacy, was published in 1976 and led to a syndicated newspaper column, syndicated public radio show and web site. In 2006, Long Island University awarded him an honorary doctorate as “one of the country's leading drug experts for the consumer.” .
Managing Diabetes

Download 8 pages on the pros and cons of the various medicines used to lower blood sugar and a wealth of details on non-drug approaches such as diet, supplements and special foods.

Managing Diabetes
  • Olgun A, "'Metformin-resistant' folic acid producing probiotics or folic acid against metformin's adverse effects like diarrhea." Medical Hypotheses, Sep. 2017. DOI: 10.1016/j.mehy.2017.07.009
  • Foss MT & Clement KD, "Metformin as a cause of late-onset chronic diarrhea." Pharmacotherapy, Nov. 2001.
  • Hsu WH et al, "Effect of metformin on kidney function in patients with type 2 diabetes mellitus and moderate chronic kidney disease." Oncotarget, Jan. 12, 2018. doi: 10.18632/oncotarget.23387
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How long after stopping Metformin would you have relief from diarrhea?

When I first became diabetic , I was put on Glaucophage XR 500 mg. twice a day. Then the insurance company I was with would not pay so had to switch to metformin. That is when my bathroom woes started. So one day when I was so frustrated the thought came back to me to start the Glaucophage XR again, as my insurance paid. Then about a couple of months ago, I went to get my Glaucophage XR refilled and the druggist informed me that the only manufacturer that was making it….stopped. I cannot get the brand name, had to go back on metformin XR 500 mg. 2 x daily and the diarrhea has came back full force. Do you have any info of another manufacturer? hope you can help!!

Everyone that is on Metformin should switch to the extended release version. The gastric problems are greatly decreased. Read the results of drug trials for regular and extended release. When the extended release version came out, I looked up the info on both, and asked my doctor to switch me over. Fixed my problem. He switched all his patients over. Pays to do your own research.

After starting Metformin I experienced cramping, diarrhea and gas. It got so bad I had to take time off from work. My doc told me to stop the drug, so I did. The side effects were slow to go away so I saw a gastroenterologist who diagnosed diverticulitis. It was so bad that I needed a colon resection. My doc told me it was a coincidence and not related to the metformin. I’m not sure what to believe. Is it a coincidence that the metformin and diverticulitis happened at the same time? Has anyone else experienced this?

Metformin led to kidney damage which eventually led to my Mom’s death!
This drug should not be on the market!
There are other, safer drugs available. Sadly, the side effects were too severe for my Mom to tolerate, and they did not lower her type 2. Mom eventually ended up on insulin.

I had high blood sugar prior to, and just after, hernia surgery. They wanted to put me on Metformin temporarily while in hospital, and I told them “No way! It destroyed my Mom’s kidneys and killed her.” The hospital Dr said “Not a problem. That does happen, and you should never take it if it did that to your Mom.”

Had a coupe of shots of insulin only. Now 3 months after surgery my blood sugar is normal again!
Wish the FDA would do their job and pull harmful drugs like this from the market! My poor Mom would still be here, and she would not have suffered all the severe side effects from this horrible drug too!

Topical metformin is used for excessive facial hair growth in women…but does that mean that it might interfere with hair growth on the scalp, as it is absorbed through the skin?

There is another very serious side effect of metformin that I discovered after only being on it two weeks – it severely depletes your vitamin B12 levels. Mine was so severe and so sudden that I could barely sit or stand up. I needed a few months of B12 shots to get back to normal.

I was placed on 500 mg of metformin in 2012 because of a rising A1c. After two weeks I was disoriented, suffered short and long-term memory loss. I had to take off from work (dentist) and the metformin was discontinued. The dosage was decreased to 250 mg, then to 125g (cutting up pills) with the same result. Would this have had anything to do with type III diabetes? I have two generations of Alzheimer’s disease behind me.

Metformin & diarrhea

Try METFORMIN ER. Works for me.

It is the combination of carbs and Metformin that cause intestinal distress. If you switch to a very low carb diet…..a great choice for diabetics… generally will not have the side effects mentioned. In fact, if you switch to eating a very low carb or keto diet and stick with it, you may find you will eventually not need the Metformin!

I had the exact opposite experience with metformin. After starting on 500 mg twice a day, my poops became harder! Now I sit on the toilet for 30 seconds, and seldom have to wipe more than once. No other side effects, either.

I’ve only tried Metformin twice. Each time same results:: Diarhea so bad I became dehydrated and unable to move. I could only lie in bed and try to breathe. Each time , I had to call for an ambulance because this was so bad I could do nothing. I refuse to take it again, and so far managed by diet and exercise to go from 11.9 to 7.9 A1c…Not perfect, but best I can do, without a medication that makes me so ill.

Anybody have thought about and\or tried BERBERIN instead of METFORMIN ? I’ve read it has the same antidiabetes effects of metformin without all the advers effect of metformin

Berberine can lower blood sugar is a similar manner. 500 mg 3x day with meals.

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