Metformin is one of the most prescribed drugs on the planet with over 120 million people taking it for diabetes management, but that doesn’t mean it’s the most popular.
Unfortunately, metformin also has one of the lowest “patient adherence” rates, because of its side effects which can appear within hours of taking your first dose. While there are actually many positive qualities about this drug compared to other diabetes medications, metformin side effects can be remarkably uncomfortable, disrupting your daily life.
In this article, we’ll look at how metformin works, the most common side effects, how to alleviate those side-effects, and why it’s the most prescribed despite causing so much discomfort for patients.
Table of Contents
What is metformin?
Metformin, also known under the brand name “Glucophage,” is an oral diabetes medication in the “biguanide” drug class, first introduced in 1957 to treat type 2 diabetes and improve blood sugar control.
It works by reducing the amount of sugar your liver releases throughout the day, and it increases your body’s sensitivity to insulin. It can also reduce the amount of glucose that is absorbed from the food you eat, which in turn reduces your blood sugar levels after eating.
Benefits of metformin
Metformin is often considered the “first line of defense” for a patient newly diagnosed with type 2 diabetes, explains the American Diabetes Association.
The biggest benefit of metformin is the fact that it does not directly cause hypoglycemia; however when paired with other diabetes medications that do lower blood sugar, metformin could result in low blood sugar until those other medication doses are reduced to compensate.
Here are all of the known benefits of metformin:
- It increases your sensitivity to insulin
- It reduces the amount of glucose produced by your liver
- It reduces the amount of glucose absorbed from the food you eat
- It doesn’t put additional strain on your organs
- It doesn’t cause weight gain
- It’s very affordable
- It doesn’t cause hypoglycemia (unless combined with other diabetes medications like insulin)
- It can reduce your appetite
- Reduced appetite can lead to weight-loss
- It can lower your cholesterol levels
The most appreciated quality of metformin is that it does not cause hypoglycemia in patients with type 2 diabetes who are not taking insulin injections, because it does not increase your insulin production like many other diabetes medications.
While it was designed for people with type 2 diabetes, people with type 1 diabetes struggling with severe insulin resistance can take it for, too. However, when used by patients taking it “off-label” for type 1 diabetes, it could lead to hypoglycemia because it would decrease your needs for insulin via injection or pump. This would be managed by working with your healthcare team to adjust your insulin doses.
Side effects of metformin
Let’s get back to that remarkably low “patient adherence” rate — the reason for this is not a mystery.
- Diarheea (varying from mild to severe)
- Flatulence
- Nausea or vomiting
- Bloating and constipation
- Overall uncomfortable stomach
- Heartburn
- Headache
- Weight loss
Unfortunately, metformin’s side effects — documented in the journal Diabetes, Obesity and Metabolism — usually appear quickly after your first dose and while they can improve for some after a few weeks, others may find they persist.
That being said, some patients may not experience uncomfortable side effects until they’ve been taking the drug for months or a year.
Some patients will experience none of these side effects and will tolerate the drug especially well compared to the patients who find themselves constantly running to the bathroom. There’s no way to predict who will tolerate the drug well and who will not.
Why all patients taking metformin need B12 levels tested annually
Long-term use has shown in recent research to result in vitamin B12 deficiency for some patients. Left untreated, B12 deficiency can cause significant nerve damage, leading to a diagnosis of peripheral neuropathy.
If a doctor isn’t aware of this risk, they could misdiagnose the cause of a patient’s neuropathy as the result of high blood sugar levels when it may be the side-effect of metformin.
This nerve damage is irreversible, but further damage can be prevented by supplementing with a regular dose of vitamin B12. All patients taking metformin should have B12 levels tested annually. Any patient with inadequate levels should be placed on a B12 supplement immediately.
Can metformin cause lactic acidosis?
There have been a significant number of studies on metformin’s risk of inducing lactic acidosis — a state in which lactic acid builds up in the body, which can be fatal. But the greater majority of studies concluded without any cases of lactic acidosis according to “The Phantom of Lactic Acidosis due to Metformin in Patients With Diabetes” in the American Diabetes Association’s (ADA) Diabetes Care journal.
The risk of metformin causing lactic acidosis is actually so rare that the ADA says the risk is zero.
“The number of documented cases of metformin-associated lactic acidosis is small when one considers how widely metformin is used,” explains the ADA. That metformin has been used safely in patients with contraindications can be viewed as evidence that it does not cause lactic acidosis.”
The report goes on to explain that — like most drugs when taken in dangerously large quantities –metformin can lead to fatal lactic acidosis when overdosed.
“Cases of lactic acidosis from metformin overdoses, particularly in young people without risk factors, suggest that metformin can cause lactic acidosis if given in large doses.”
Patients at greatest risk for developing lactic acidosis while taking metformin are those with other conditions including kidney or liver issues, a history of heart attacks or acute heart failure, and patients who drink alcohol frequently. When discussing metformin with your healthcare team, be sure to express any concerns to your doctor.
Reducing metformin side effects
Fortunately, there are a few things you can do to alleviate, lessen, or altogether prevent the stomach distress caused by metformin.
Take your dose during your meal, not before
The first is to take your metformin dose halfway through eating your meal rather than before you start eating. Patients report far less stomach distress if there is already food within their stomach by the time their metformin dose is being digested, too.
Start with a very small dose
By starting with an extremely small dose, instead of the full dose your doctor would normally prescribe for your height and weight, you may be able to drastically reduce those initially uncomfortable side effects. Talk to your doctor about adjusting your doses in order to give your body time to acclimate to the drug.
Ask for the “extended release” version
Too often, doctors prescribe the regular version without any consideration of the extended-release (ER) version. By taking the ER version, each dose is being introduced over the course of hours and hours versus all at once, which significantly reduces the unwanted gastric side effects. While it does cost more, it could greatly metformin’s side-effects. However, you will need to try the regular version first. This is so your doctor can tell your insurance company you tried it, and it wasn’t the right medication for you. Then they will be more likely to cover the more extended “ER” version.
Combine it with other diabetes medications
If you and your healthcare team intend to start you on a GLP-1 drug like Victoza or Byetta, the side-effects of metformin can actually give balance to the constipation side effects of most GLP-1 drugs. By taking both drugs as part of your diabetes management plan, the side-effects of both drugs essentially balance each other out.
Try something else
Again, there are simply some people who do not tolerate metformin. If you find you cannot bear to endure the side effects, talk to your healthcare team. If you choose to stop taking metformin, your healthcare team can help you find a different type of diabetes medication to improve your blood sugar levels.
Monitor vitamin b12 levels
For patients who take metformin long-term, your vitamin b12 levels should be tested annually. Research shows that a small percentage of patients taking metformin develop deficient b12 levels which can be managed with supplemental b12 vitamins. Discuss this with your healthcare team if you’ve been taking metformin for more than one year.
Metformin might help to lower your blood sugar levels, but your quality of life matters, too. The side effects of metformin can be brutal, and for many, worth avoiding. There are many, many, many other diabetes drugs out there, and most of them are not like metformin at all. Don’t give up and don’t just quit the drug without talking immediately with your healthcare team to find a better alternative for you.
You shouldn’t take metformin if…
Like most medications, there are a few types of patients who shouldn’t take metformin. For metformin, the concern is based largely around the fact that it can raise your risk of producing too much lactic acid. Clearing that lactic acid from your body requires healthy organ function!
If you have diagnosed kidney or liver issues: Your liver and your kidneys both play a critical role in clearing metformin from your body. If your kidneys or liver are already struggling to function, you wouldn’t want to add to their workload by taking metformin.
If you have had a heart attack or acute heart failure: Serious heart conditions can affect how much blood is pumped to your kidneys, which can reduce your overall kidney function. Because the kidneys play a crucial role in clearing metformin from your body, patients with a history of heart issues should not take metformin.
If you drink alcohol often or in great quantity: Again, because metformin relies on the function of a healthy liver and kidneys, a person who drinks large amounts of alcohol on a regular basis would be putting themselves at an increased risk for other issues if they took metformin. If you are concerned about your personal alcohol consumption, take a look at these helpful resources listed at Alcohol.org.
Suggested next posts:
If you found this guide to Metformin side effects useful, please sign up for our newsletter (and get a free chapter from the Fit With Diabetes eBook) using the form below. We send out a weekly newsletter with the latest posts and recipes from Diabetes Strong.
I was wondering if Metformin takes time to rebuild effectiveness after a period of eating higher-carb meals? For example, I’ve been on Metformin for a year and I have eaten consistently well during that time, but Christmas and New Year consisted of some pretty poor eating on my part but I was taking Metformin throughout. I’m now back to regularly scheduled eating but have found that I’m not reaping the typical benefits of proper eating while on Metformin. Does it take some time for the effectiveness of Metformin to rebuild after a period of poor eating?
Hi Jenny!
It’s really not an issue of your metformin not working as much as it’s about your diet changing. Your metformin was dosed properly for your non-Holiday normal diet. And then you ate more calories and carbs for a couple of weeks thanks to the holiday season (and the dark cold winter, if you live where I do!)…and so your metformin dose simply wasn’t high enough to keep your blood sugars in range with that increase in your diet.
Now that you’re back to your normal routine, I suspect you’ll find your blood sugars will go back to your normal range within a week or two of eating more balanced.
Let me know if this is helpful! If your BGs continue to run high, that’s worth making a call to your doctor to discuss adjusting your medication doses.
I too have suffered from diarrhea for at least four months after having my dose of metformin doubled. As of yesterday I was taken off of it for the next three months. A colonoscopy has been scheduled just to make sure that it’s nothing else. It’s destroying my life. No energy etc.
I have been on metformen for maybe 15 years. Iasked my doctor if it was safe and he said yes but I was reading some of the side effects and seem to have a few of those like shortness of breath, extreme exhaustion tired all the time. Im76 years old and always had lots of energy Until the last couple years. He added B- 12 shot once a month about a year ago Most days I want to just stay in bed. I know my age might have something to do with it but not to the extreme that I feel I’m also lightheaded and have occasional dizzy Spells I just want to feel better
Not feeling well is so frustrating. My suggestion would be to take these concerns to your doctor and have a good discussion. It might not be the Metformin but something completely different, regardless it should be looked into. If you find that your doctor doesn’t listen (unfortunately that happens sometimes) I’d recommend you look for another doctor
My 14 year old daughter was recently prescribed Metformin. She has been having terrible stomach pains. She takes the medication right after eating supper each night, but is really struggling. Are there any foods that could help with the stomach pains? I’m having her try eating yogurt with good probiotics and wonder if Sweet Acidophilus milk might help.
Hi Robin!
Food isn’t going to help this. If you read this article thoroughly, you’ll see that upset stomach is a common side-effect, and the best solution is to ask her doctor for the “extended release” version. Your insurance will require that she tried the cheaper basic version first, but a doctor can document that she didn’t tolerate well and that she needs the “extended release” version instead.
Contact your daughter’s healthcare team ASAP!
I’m 54 yr old, 5’4” and 236 lbs… I’m healthy but know that I really need to drop to at least 200lbs. I eat low carb and swim 1 hour 5 days a week and can’t loose not 1 lb! I”m thinking that Metformin could help can I take small dose before bed, I’m ok waking up to do my business then go back to sleep. What dose is good to start with?
That’s a discussion you’d have to have with your doctor. He/she should go over it with you when the prescription is written
I have been on Metformin ER since March and I am having muscle pains in my arms and shoulders that is steadily getting worse!
That does not sound sustainable, please consult with your doctor as soon as possible. If your joints feel stiff it could be a frozen shoulder (https://diabetesstrong.com/frozen-shoulder-diabetes/) or something else altogether. However, your doctor should be able to guide you
I am feeling the same sympton and I do not know what can I do. Please, would you like tell me something.
I was diagnosed 7 days ago and put on Metformin 500mg. My doctor explained the diarrhea issue, but didn’t warn me of the stress associated with it. I have uncontrollable episodes 4-5 hours after each dose. I am a professional with business meetings. I can’t concentrate with the fear of a unwanted episode. How long before I can request the ER version?
I would suggest reaching out to your doctor ASAP and request the ER version. No need to suffer
Can you help me?
My husband has been on Metformin for Type2 Diabetes for almost 2 years
He has become very bad- tempered and uncooperative so much so I feel I can no longer live with him . Could this be due to this drug or a low blood sugar which usually between 5 and 6 before and after meals.
We are both76 yrs. old
Mary!
I’m so sorry to hear what you’ve both been going through. Can low blood sugars make a person angry? Absolutely. However, technically metformin cannot cause low blood sugars. I would guess that something else is going on and I hope you can take action sooner than later in seeking professional help for both him and yourself. He may need a deeper evaluation from a doctor? Big changes in a person’s personality like that shouldn’t be taken lightly and could signify a slew of other potential health issues.
Don’t forget to take care of YOURSELF in the meantime — maybe talking to a therapist could be helpful? And make sure you are safe. Reach out to friends — don’t go through it alone.
Wishing you the best,
Ginger
Since diabetics often suffer pain, it might be helpful to look into any pain medications your husband takes. Since the opioid crisis many doctors now prescribe Tramidol for pain. My husband and I both found ourselves to be short tempered and irritable. Ask you doctor.
in response to laura beltran 4/30 of being tired that was what i was, I researched it and added blood lab for b-12, it was single digits. i now take b-12 oral prn and make sure that it is tested every 6 months. i have been on metformin for 15 years i am approaching 80 yo.
Do you have any suggestions for someone that has continued diarrhea after 3 years of taking the Metformin XR? It’s quite annoying because when I have to go I have to go ASAP and I have had some close calls. Sorry to be so abrupt but I’m getting very tired of this side effect as it makes it difficult to plan outings. I don’t really have a time after taking my dosage that it will happen so I could plan around that amount of time. It’s summer time and hiking season and I’m afraid to participate. I am in a research study and won’t be able to get a different drug for another 2 years as Metformin is part of the study. The only thing that helped was taking an iron supplement while I had an issue with low iron stores. That issue is resolved now and I no longer need to take iron. Now my body has returned to the same.
Hi Becca!
If you’re still having severe digestion issues on metformin after 3 years, I would think you could be removed from the study due to an “adverse reaction” to the drug. You shouldn’t have to suffer!
I also just want to pose the question: are you sure your stomach issues are from metformin? Just in case it might be something you’re eating? Gluten?
I’m sorry I can’t be more helpful!
I had been taking metformin for 2 years on my 2nd year I developed severe diarrhea and every primary physician just gave me diarrhea meds or over the counter meds I was truly dieing by the 10th month of this condition until I noticed my stools had small white specks and later I started seeing stringy things in my stools so I researched for about a week on the internet and found out I was infested with pinworms that was so disgusting I soon realized that my diarrhea always happened right after I took the medication, so I stopped taking it and the over the counter meds didn’t work so I looked up home remedies online and it worked the pinworms came out all at one in a braided stool. So I peeped one sample and put rubbing alcohol and put in a clean compact inside a ziploc bag so the doctors didn’t want to see the specimen or photos I took during the time all this was happening to me. I was very upset I had to cure myself and spend some much money on incompetent doctors that won’t don’t care about their patients. So I had lost all my good bacteria from the diarrhea and the bad bacteria took over my intestines now that I’m cured of that I had damage to my large intestine. Colonoscopy fountain a polyp and had a biopsy thankfully it was negative but I need surgery for my prolapsed colon and I still have to wear disposable undergarments because my muscles in my intestines were left so week I have accidents and a lot of mucus drainage and now it’s clear watery drainage. Sorry to be direct but everyone should know what to look for and the out come from taking metformin when this is never disclosed to the patient taking this life threatening drug so beware!!!!!!!
Gee thanks for sharing. TMI not even remotely related to the discussion or the medication. Have some discretion, metformin sure as heck didnt infest you with worms!
Sorry for the aweful worms and what not that’s happened to you but as someone who has graduated with a major in science. I can assure you, that metformin did not give you worms and cause you to loose muscle strength in your rectum. The intestines dont really support the muscles as your rectum is composed of more muscles, which isn’t a side effect. The only side affect that is common is severe diarrhea by metformin and as mentioned above they made an extended release version for those who suffer with the side effects and it says it’s best to take the medication while your eating like halfway through your meals and not before or after. I’m sorry a doctor is hard to find in your area. Please, consult with someone somehow to get insurance if you dont have it or ask your insurance for health providers in your area and explain to them everything or simply show them the message on here.
I was recently diagnosed as having Type 2 diabetes. I am taking Metformin. Recently I’ve discovered I cannot eat much dense protein (chicken, beef, etc.), else it gives me sulphur burps and diarrhea. I’m thinking it’s something to do with the Metformin. I think I read somewhere that Metformin slows down the digestive process, to help reduce blood sugar spikes. I’m thinking that’s causing my body to be unable to handle a lot of dense protein, because it can’t process it quickly anymore. Am I right? If so, how can I get around this limitation? Soy burgers from now on? 😀
Jared!
Metformin absolutely wreaks havoc on the digestive system. You’ll see in the article a section about the “Extended Release” version. Your insurance company will require that you start on the normal version, but if you report to your doctor how much digestive trouble you’re having with metformin, they can usually get you insurance coverage for the Extended Release (ER) version which is much gentler on the stomach!
If I were you, that’s what I’d try first. (That being said, I LOVE a great veggie burger!!!!)
Hello
Started Metformin 10 days ago and have increased my dose to twice daily with my insulin pump working along side it , I seem to swing from diarrhoea to constipation , it’s driving me nuts as I can’t plan my day as I don’t which I’m gonna get on which day . Any suggestions would be greatly appreciated .
Hi Linda!
I’m not sure why your body is juggling back and forth between diarrhea and constipation but many folks who struggle with diarrhea on Metformin do better when they switch to the “Extended Release” version of the drug — there’s more detail about this in the article. I would talk to your doctor ASAP and request a prescription for the “ER” version!
Hello, well if it is the metformin I’d consult your doctor ASAP, and tell them all the trouble your having, because it could be the metformin or something else never know until you go through trial and error with your physician. But for me personally I am 21 years of age and have never taken metformin not need to right now but I too suffer from bowl movements that are very different and painful. A few weeks diahherea a few normal then some constipation but mostly soft stools and I told a doctor at urgent care and she didnt diagnosed me but she did say it sounds like it could be ibs, so you never know really. All I know is since being a teen I’ve had very painful stomach issues and no doctor until her had told me it could be ibs which I had a feeling it was from my nerves and anxiety. So, I hope you find a solution to your problem soon.
I need your help, I have tried all types of medformin and I get very nauseated. At this moment I feel so weak and have not been able to get out of bed. If someone can give me some advise PLEASE.
Started with 500, then 1000 and now 2000 and it always the same.
Is there any other medication out there?
Sorry to hear that your medication isn’t working for you. Yes there are other medications available, but please don’t discontinue or switch medication without consulting your doctor or another qualified trained medical professional
After taking Metformin in the morning I find myself rushing to the bathroom within three hours, but not everyday. My everyday breakfast is always cereal with extra walnuts and was wondering if adding more protein to my breakfast would help with diarrhea?
Hi Cindy!
You’ll find in the article that this is VERY common — and there is something you can do about it with your doctor’s help. Report your severe diarrhea to your doctor and ask for the “ER” extended release version of the drug. Your insurance company will require you to prove that you tried to normal version first, but with your doctor’s note that you responded poorly to it, you should be able to get coverage for the “ER” version. Many patients report that the “ER” version resolves the issue of diarrhea. Good luck!
Thank you Ginger. I was able to take the ER version and did well with it for a while, but found it difficult to swallow due to the larger size, therefore my doctor prescribed the regular and smaller metformin medicine which is causing the problem.
I am type 2 and was prescribed the ER version of metformin and it’s been about 3 mos now. The constant diarrhea has not subsided and my Dr said I could take imodium. It doesn’t help a whole lot and my goal is to decrease the amount of meds I take not increase! Anyway I’m giving in three more months and it that time I am going to be faithful in my low carb intake. I’m hoping my A1c goes down enough to at least lower the dose 🙁
I just wanted to clarify the part of the article that references Metformin Extended-release. The article states that providers “prescribe the regular version without any consideration of the extended-release (ER) version.” As an RN who was recently diagnosed with DM2, I can say that for most insurances to pay for the Metformin ER version, the Metformin orginal must be tried first. This is the same for Rheumatoid medications as well. The cheaper version must be tried first before the more expensive versions are prescribed. Thanks.
Hi Tara!
Thank you for explaining that crucial detail — I will add it to the article.
Ginger