What Are the Common Side Effects of Metformin?

Our Chief Medical Officer explains

Learn more from Dr. Sajad Zalzala, MD

Video Transcript

This is Dr. Z, Chief Medical Officer with AgelessRx. I get asked all the time, what are the side effects of Metformin?

Well, as a physician who has written for Metformin to thousands of patients, I can confidently tell patients that metformin is a very well tolerated, safe drug. Probably one of the safest that we have. We know a lot about the safety profile of metformin, and that’s why I love prescribing it.

When it comes to side effects, the most common by far is gastrointestinal stomach issues. Most patients will report loose stools, sometimes diarrhea, stomach cramps, a little bit of nausea. And there are many things that can be done to either reduce the likelihood of getting these side effects or to treat the side effects if they do occur. The first thing is, I always prescribe a standard release, unless somebody specifically wants the immediate one. I always tell patients to take it with a meal. Largest meal of the day, if possible. If not, any meal will do. And of course, the most important thing is starting low and going up slow.

If side effects do happen, they’re usually they’re temporary. They only last maybe a week / two weeks. But again, it almost always subsides in probably 80-90% of patients who do get the side effects. So if you do happen to be one of the unlucky few that do get the side effects, just stick with it and usually all subside on its own.

There are there are a few things that I recommend to patients. I typically try to recommend over the counter remedies first.
For example, if you’re having diarrhea loose stools, you could try a little bit of a Imodium available over the counter. If you’re having gas or bloating from it, Simethicone or Gas-X can work really well. If you’re having some nausea from it: ginger chews. Gin-Gins. These are my favorites. You can pick those up at a health food store or on Amazon.

There are some cases where those may not be effective enough, in which case I’ll pull out the prescription pad, call out a prescription for a patient. I remember there was a young lady who had some colon issues to begin with, really wanted
to try Metformin and so we tried the over the counter didn’t work at first. Combination of Zofran and Bentyl
(dicyclomine) really did the trick, got the patient over the hump. After the first two or three weeks of her intestines adjusting to the medication, she was able to tolerate and is still on it [Metformin] to this day. So there are a lot of things that can be done.

We have a blog article about this that expands on this at AgelessRx.com. If you have any questions, you can also contact us. This is Dr. Z, Chief Medical Officer, AgelessRx.

Maybe you’ve only just heard all the buzz about Metformin. Maybe you’ve just started taking your first doses—or you’re already a Metformin master.

No matter what your relationship with Metformin is, knowing and understanding which side effects you are most likely to experience is probably among your chief concerns.

Of course, reading the label or perusing the manufacturer’s website is one thing, but it’s not quite as nice as going directly to the source and asking a medical expert. And who could be better than our very own Dr. Sajad Zalzala, Chief Medical Officer of AgelessRx?

Dr. Z is an experienced primary care doctor focused primarily on helping people prevent and delay chronic conditions. He has not only helped countless people achieve longer, healthier lives, but he has also been prescribing Metformin to thousands of patients across a career that has spanned over 20 years.

What you should know about Metformin side effects

The first thing you should know is that Metformin is a very well-tolerated and safe medication. In fact, it is probably among the safest medications available: the World Health Organization has included Metformin on its Model List of Essential Medicines, a catalog of some of the safest, most effective and most economical medications in the world. What makes this particularly remarkable is that Metformin has also been researched extensively and its safety profile is thus very well defined as compared to other medications.

As such, any incidence of side effects tends to be mild and often goes away as your body gets used to the current dosage you’re taking – and that’s if you experience side effects! About 80% of our patients in our studies reported no side effects at all.

If you happen to be among those who do experience side effects, here are some of the most common side effects you may experience and some ways you can avoid or mitigate them.

Research suggests that Metformin may activate longevity pathways and reduce the risk of age-related diseases like diabetes.

Most common side effects of Metformin

The most commonly reported side effects of Metformin have to do with gastrointestinal (stomach) issues. Most patients who experience side effects report one or more of the following:

  • loose stool or diarrhea,
  • stomach cramps,
  • gas and bloating,
  • nausea,
  • and/or B12 deficiency

Again, these are usually reported within the initial starting phase of your dosage (soon after you begin taking Metformin regularly) and tend to go away on their own.

Infographic illustrating areas of the body where Metformin side effects can occur

How to avoid common Metformin side effects

Fortunately, though, we don’t have to just wait around and let our bodies do all the work for us. There are many simple steps we can take to both reduce the likelihood that we will experience these side effects at all and to mitigate them if we do experience them.

  • Try Extended Release
    First, the incidence of even mild side effects can be reduced by prescribing extended-release Metformin, rather than faster-acting, more immediate prescription. If you start to feel any of the above-mentioned gastrointestinal issues, this is the first and quickest option you should check. If you are on the faster acting prescription, ask your healthcare provider about the extended-release option. Those who have Metformin prescriptions through AgelessRx likely won’t have to worry about this, as you are almost certainly on the extended-release option unless you have requested otherwise!
  • Take with Food
    Another way to reduce the likelihood that you will experience Metformin side effects is to take Metformin with a large meal. We recommend taking it with your largest meal of the day (which is dinner for most), but if that’s inconvenient for you, taking it with any meal will be just fine.
  • Start with a Lower Dosage
    But perhaps the most important thing we can recommend is starting at a low dosage and slowly ramping up as your body adjusts to the medication. This will ensure that your body is not shocked by a larger initial dose and that no potential side effects are exacerbated.

Are you curious if Metformin is right for you? Our dedicated longevity experts are available to answer your questions.

How to treat common Metformin side effects

If you do experience these side effects, rest assured that they typically last for only about a week or two.

However, these side effects usually subside on their own over time. So don’t let these minor side effects get you down or off track: sticking with your prescribed dosage is almost always the best way to go.

During this time, we try to recommend at-home remedies or over-the-counter treatments as your first order of treatment for these side effects.

  • For those experiencing loose stools or diarrhea, try taking a low dose of Imodium. This simple medication can be purchased over the counter at most pharmacies or retailers and is an effective way to reduce these symptoms. However, keep in mind that this is a short-term solution, as Imodium should not be taken for more than a few days in a row.
  • Similarly, gas or bloating can be treated with simethicone, which is often sold under the brand name of Gas-X. This has shown to be an efficient, inexpensive relief for these symptoms and can be taken as needed.
  • Anyone who regularly experiences nausea may also be familiar with ginger chewable candies. As ginger is a natural stomach soother, it has been widely used throughout history as an antiemetic (anti-nausea) remedy. There is certainly no shortage of ginger candies, which are popularly sold under the brand name Gin-Gins (among others), so relieving nausea symptoms should be just as easy as finding ginger candies at any of your local stores.
  • Additionally, some who take Metformin experience vitamin B12 deficiency, though it’s important to note that B12 deficiency may not be directly caused by Metformin. People at risk of low B12 levels should consider supplementing with B12 when taking Metformin. Many prefer taking Methylcobalamin (B12) at 500-1000mcg, which is generally the most widely available, over-the-counter option. For those who prefer a stronger B12 boost, consider augmenting your Metformin prescription with vitamin B12 shots offered by AgelessRx.

If you are in a rural area or just hate going outside, we’d like to mention that all of these remedies can also be purchased from Amazon and other online retailers, while B12 can be purchased directly from our longevity platform.

In some rare instances, over-the-counter solutions may not be quite enough to relieve the gastrointestinal side effects of Metformin. In these cases, it may be time to have a talk with your healthcare provider, who may recommend prescription-strength medications.

From Dr. Z’s clinical experience, he has found that a combination of Zofran and Bentyl (dicyclomine) was able to curb persistent gastrointestinal symptoms. It should be mentioned though that this option was explored only after exhausting relevant over-the-counter options. Additionally, it may be worth noting that there were pre-existing gastrointestinal issues before prescribing Metformin.

For further information

Though gastrointestinal symptoms like diarrhea, cramps, gas, and nausea are the most common side effects of Metformin, we still encourage you to read through the full list of side effects for Metformin before you consider trying it. We also have several fantastic blogs available for you to read on our website that cover these topics in fuller detail.

And, of course, if you have any questions or concerns about Metformin that are not covered here or on our website, please don’t hesitate to contact us.

The power to take control of your health is at your fingertips. Begin your free medical evaluation to get started with Metformin.


Christofides EA. Clin Diabetes. “Practical Insights Into Improving Adherence to Metformin Therapy With Type 2 Diabetes.” 2019.

FDA. “Drug Approval Package: Metformin.” 2005

FDA. “Drug Approval Package: Imodium.” 2018.