Metformin is the most commonly prescribed oral drug for diabetes. Of course, if you or a loved one receives treatment for diabetes, you probably already knew this.
What you may not know, however, is that the benefits of metformin don’t begin and end with diabetes.
Metformin lowers blood sugar levels by decreasing the amount of glucose the liver produces, diminishing how much is absorbed and enhancing insulin sensitivity.
That’s amazing for people with diabetes, but greater insulin sensitivity has positive ripple effects throughout the body. Many benefits of metformin come from its off-label uses.
We’ll get more into that in a minute, but as a quick spoiler, off-label uses for metformin include managing gestational diabetes (diabetes that develops during pregnancy), addressing weight gain issues caused by antipsychotic medication and treating and preventing polycystic ovary syndrome (PCOS).
We’ll break down the surprising benefits of metformin below.
Metformin belongs to a group of drugs called biguanides. By “group,” we mean it’s the only one. There were two more, but in the ‘70s, the others were withdrawn from clinical use for causing lactic acidosis (lactic acid in the bloodstream).
The official use of metformin is to lower blood sugar (or blood glucose concentration in science talk) for people with type 2 diabetes. It does this by improving the body’s response to insulin and decreasing the amount of blood sugar produced by the liver and absorbed by the intestines or stomach.
Metformin also makes muscle tissue more sensitive to insulin so glucose can be used for energy, according to the American Diabetes Association.
The relationship between glucose and insulin is tricky to grasp, so here’s a quick explainer: Insulin helps move glucose from blood into cells, where it can be used as energy. So as glucose rises, so does insulin.
Think of insulin as the front-of-house staff at a hot new restaurant in town (called Your Cells) and glucose as the patrons.
When things are balanced, the staff (insulin) lets a steady — but not overwhelming — flow of people (glucose) into the restaurant (your cells).
When there’s not enough staff (insulin) to properly manage the flow of patrons (glucose), people are forced to wait outside and take up the sidewalk (your bloodstream), which creates a bit of a frenzy.
For a restaurant, this can mean turning down good business. For your body, it means high blood sugar.
And it goes both ways. When the staff (insulin) allows too many patrons (glucose) into the restaurant (your cells), it can make the restaurant look dull from the outside because there’s no traffic on the sidewalk.
For your body, this is low blood sugar.
Metformin (and the brand-name versions, Riomet® and Glucophage®) isn’t used by people with type 1 diabetes, an autoimmune disorder wherein the body does not make insulin.
Metformin can have side effects, though they’re usually mild.
The most common side effects are gastrointestinal (everyone’s favs: diarrhea, bloating, stomach pain, gas, indigestion and constipation). These affect up to 30 percent of metformin users.
In U.S. clinical trials, about four percent of participants couldn’t continue metformin due to adverse effects.
While rare, lactic acidosis (when lactic acid, the same thing that makes you sore after a workout, builds up in the blood) can be a side effect in those with poor kidney or liver function or due to an overdose of metformin. The incidence of lactic acidosis is one in 30,000, so it’s not something you should lose sleep over.
Now, for the question that brought you here: What are the benefits of metformin? There are actually a bunch of pretty cool benefits of this diabetes drug.
Here’s a sneak peak of what metformin can do:
Aid in weight loss
Offer anti-tumor effects
Reduce the risk of heart disease
Help manage gestational diabetes
Improve cognitive function
Help with PCOS and infertility caused by PCOS
Possibly extend lifespan
Read on for the nitty-gritty of all metformin can do (it’s honestly kind of a show-off).
Metformin is considered weight-neutral, meaning it isn’t related to drastic weight gain or loss. However, studies show it can result in modest weight loss in people with diabetes.
Antipsychotic medications can increase blood glucose levels — this often causes weight gain and, to a lesser extent, diabetes.
Since metformin has the opposite effect and lowers glucose levels, the drug can effectively counter weight gain caused by antipsychotics. This is excellent news for anyone deterred from taking their antipsychotic medication for fear of not fitting into their clothes.
Remember, most metformin studies are conducted on those with diabetes. So there’s not much research on whether it causes weight loss in non-diabetic individuals.
That said, a 2013 study on people without diabetes who were overweight or had obesity found that those taking metformin lost between 5.6 and 6.5 percent of their body weight. In contrast, the control group gained 0.8 to 3.7 percent.
However, this was a smaller study, and more research on the effects of metformin on people without diabetes is needed.
One of the most intriguing benefits of metformin is that it seems to have anti-tumor effects in certain tumor-related cancers, including ovarian, breast, colon, prostate and colorectal.
One analysis found that metformin “reduced cancer incidence and mortality in patients with diabetes, with overall cancer incidence reduced by 31 percent and cancer mortality reduced by 34 percent.”
It’s thought that metformin has anti-tumor effects because it lowers insulin levels and keeps tumor cells from multiplying. But again, more research is needed on metformin’s anti-tumor effect on people without diabetes.
Call it Cupid because, as a cardiovascular protective agent, metformin is good for your heart. That sounds hardcore (and it is), but more simply put, the drug can help prevent cardiovascular disease and heart failure.
Cardiovascular complications are the leading cause of death in people with diabetes. People with diabetes are twice as likely than someone who doesn’t have the condition to have heart disease or a stroke.
Research findings on metformin and heart health are mixed. In one study, type 2 diabetes patients showed a “significant reduction” in a cardiovascular composite when treated with metformin compared to those treated with sulfonylurea (one of the other popular diabetes medications) after five years.
Researchers think the most pronounced effects of metformin on heart health occur after continuous use for five or more years.
Gestational diabetes affects roughly 8 percent of pregnant people, according to the most recent data from the Centers for Disease Control and Prevention (CDC).
When the body can’t make enough insulin during pregnancy, gestational diabetes may occur. The condition typically resolves after birth. And while it can — and does — happen to anyone, being overweight and having obesity is linked to gestational diabetes.
Metformin may be prescribed as an alternative to insulin in cases of gestational diabetes. Though the medication crosses the placenta and can be present in breast milk, it’s still considered safe for pregnant women.
If left untreated, gestational diabetes can cause high blood sugar levels in the fetus since glucose crosses the placenta. It can result in a large baby, as excess sugar the fetus doesn’t need for energy is stored as fast. Babies born to mothers with gestational diabetes often have hypoglycemia.
This may seem counterintuitive, as hypoglycemia is low blood sugar (hyperglycemia is high blood sugar), but infants born to mothers with gestational diabetes receive higher sugar levels in utero, and so their bodies make more insulin to counter this. When they’re born and not getting excess sugar anymore, they have too much insulin, which causes blood sugar to plummet.
These babies are also at risk for obesity later in life.
Diabetes damages blood vessels and nerves, so it can affect the brain too.
According to the CDC, this can lead to various issues, like mood shifts, hormonal changes and weight fluctuation. Perhaps even more nerve-racking, it can also create problems involving memory and learning — and, over time, may contribute to serious cognitive issues like Alzheimer’s disease.
Here comes metformin again — the drug may improve cognitive function in people with diabetes.
One meta-analysis found that metformin reduced the incidence of cognitive impairment, but not specifically Alzheimer’s disease in adults with diabetes.
However, researchers noted that there is only “weak support” for the idea that metformin can prevent cognitive impairment in people without diabetes. So more research is needed there.
Like so many disorders affecting women, PCOS isn’t fully understood and is maddeningly underdiagnosed.
One thing that is known, however, is that many women with PCOS are insulin-resistant, meaning they produce more insulin than they need to. And according to a 2012 study, they’re at “markedly high risk for developing diabetes.”
The increased circulating levels of insulin have direct effects on the ovaries, including excess testosterone production and anovulation (a condition where ovulation doesn’t happen, leading to infertility).
Metformin is effective as a treatment for infertility among women with PCOS who don’t ovulate regularly. A study on 702 women found that the clinical pregnancy rate for those using metformin versus a placebo group was significantly increased.
Let’s get this off our chest: You won’t suddenly be the next Benjamin Button if you take metformin. However, early studies (on rats, not humans) show that metformin may slow aging and increase life expectancy.
This seems to result from the drug’s known antioxidant effect and its ability to improve insulin response. The theory is that it has a substantial impact on age-related diseases — aging can induce insulin resistance, causing a slew of medical conditions.
Metformin is kind of like a trendy job in Silicon Valley — it comes with lots of great benefits.
In terms of diabetes care, metformin is the go-to treatment for type 2 diabetes and is the most commonly prescribed oral medication for the condition. It’s typically taken twice daily and is available in immediate- or extended-release tablets.
Here’s what to keep in mind about the benefits of metformin:
Metformin isn’t like other diabetes medications prescribed off-label for weight loss (we’re looking at you, Ozempic). However, it may induce modest weight loss in people with diabetes. And while more research is needed, it shows promise in promoting weight loss in situations where weight gain is caused by elevated glucose levels in the blood, as is the case with weight gain from antipsychotic medications or PCOS.
Metformin shows may also help reduce the severity of diseases relating to insulin and glucose levels. This includes PCOS, certain tumor-related cancers, gestational diabetes and age-related diseases.
Side effects of metformin are typically mild and include GI (gastrointestinal) issues like gas, diarrhea or bloating. However, the FDA warns against using metformin if you have kidney disease or a kidney abnormality. It’s important that your healthcare provider monitors kidney function in each patient using metformin.
If you were looking for information about metformin and weight loss specifically, our blog post on the link between weight loss and depression might interest you. You can also learn about other medications associated with weight loss, like Celexa or Wellbutrin®.
And if you’re unsure about whether metformin is a good choice for you, talk to a healthcare professional or learn more about weight loss treatments.
Dr. Craig Primack MD, FACP, FAAP, FOMA is a physician specializing in obesity medicine.
He completed a combined residency in Internal Medicine and in Pediatrics at Banner University- Phoenix, and Phoenix Children's Hospital. He received post-residency training in Obesity Medicine and is one of about 7,000 physicians in the US certified by the American Board of Obesity Medicine.
In 2006, Dr. Primack co-founded Scottdale Weight Loss Center in Scottsdale, Arizona, where he began practicing full-time obesity medicine. Scottsdale Weight Loss Center has grown since then to six obesity medicine clinicians in four locations around the greater Phoenix Metropolitan area.
From 2019-2021, he served as president of the Obesity Medicine Association (OMA), a society of over 5,000 clinicians dedicated to clinical obesity medicine. He has been on the OMA board since 2010, currently serving as ex-officio trustee.
Dr Primack routinely does media interviews regarding weight loss and regularly speaks around the country educating medical professionals about weight loss and obesity care. He is co-author of the book, “Chasing Diets”.