Metformin for PCOS (Benefits and Side Effects)

Metformin is among the most commonly prescribed drugs in the world. It’s very effective in regulating blood sugar levels for people living with type 2 diabetes.

However, metformin is also increasingly being prescribed for people who live with polycystic ovary syndrome (PCOS). 

This article will cover everything you need to know about using metformin for PCOS.

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Key Points:

  • Metformin helps manage PCOS symptoms such as irregular periods, weight gain, acne, and infertility by stabilizing hormone levels and improving menstrual regularity.
  • While the medicine is generally safe, its use for PCOS is not FDA-approved and is considered off-label. Common side effects include gastrointestinal issues, and rare but serious side effects such as lactic acidosis can occur, especially in those with kidney or liver problems. 
  • Metformin works by lessening sugar production by the liver, reducing sugar absorption in the intestines, and decreasing insulin resistance, a common issue in PCOS. This helps with regulating menstrual cycles, reducing excess hair growth, and potentially aiding in weight loss.
  • Metformin is not a cure for PCOS, but it can effectively manage its symptoms. The effectiveness varies among individuals, and lifestyle changes like diet and exercise are also crucial.
  • It’s important to consult with healthcare providers to tailor the treatment plan, especially for those who are trying to conceive or are pregnant.

Table of Contents

Why would someone with PCOS be prescribed metformin?

Polycystic ovary syndrome is one of the most common hormonal issues affecting women of reproductive age. 

PCOS can cause the following symptoms:

  • Missed or irregular periods
  • Pelvic pain
  • Fertility issues
  • Cysts on the ovaries
  • Excess hair growth
  • Acne
  • Acanthosis nigricans (patches of thick, dark skin)
  • Insulin resistance and high blood sugar
  • Weight gain or difficulty losing weight

Metformin is increasingly used to treat the symptoms of PCOS.

Metformin comes in many brands and is taken daily (or two times each day), typically as an oral pill. 

Metformin helps to manage your blood sugar levels and fight insulin resistance, and it can even help with weight loss.

See more in: Metformin and Weight Loss: Can a Pill Help You Lose Weight?

If you have PCOS, you might be prescribed metformin because it has been shown to stabilize hormone levels and because it helps many women get back to regular menstrual cycles.

There is also evidence that extended use of metformin leads to more regular menstrual cycles and a reduction in the severity of many PCOS symptoms.

If you have PCOS and are dealing with weight gain, irregular periods, acne, or infertility, your doctor or medical provider may prescribe metformin to help you manage these symptoms.

Is metformin safe to use for PCOS?

Metformin is broadly accepted as a safe medicine, no matter the reason it is prescribed. 

It is important to note, however, that metformin for the treatment of PCOS is not officially approved by the U.S. Food and Drug Administration (FDA). Any prescription by a physician to treat PCOS with metformin is considered “off-label.” 

There is a risk of side effects that you should be aware of when taking the drug for PCOS. 

Read more in: Metformin Side Effects (Common and Serious).

The most common side effects of metformin include gastrointestinal (GI) symptoms such as nausea, vomiting, and diarrhea. 

See more in: Can Metformin Cause Diarrhea?

These symptoms tend to be mild, and most doctors recommend taking the medication with a meal to reduce the severity of these GI symptoms. 

Your doctor or medical care team may also recommend starting with a low dose of metformin and gradually increasing it over time to lessen your chances of experiencing a serious upset stomach or other side effects.

There are also very rare — and more serious — side effects such as lactic acidosis, which is a potentially fatal condition in which lactic acid builds up in the body. It’s much more likely to occur in people with kidney or liver problems, so your doctor will likely ask you about your medical history before prescribing metformin.

Long-term use of metformin is also known to increase the risk of vitamin B12 deficiency for some people, so bloodwork and supplementation of this nutrient, if needed, is sometimes recommended.

Metformin has also not undergone rigorous clinical trials in pregnant and breastfeeding women, although there is evidence to suggest that it would be effective. 

If you are trying to become pregnant and have PCOS, your doctor may prescribe metformin for you off-label because it can help to restore regular menstrual cycles and ovulation. It’s important to discuss whether it’s safe to continue taking the drug if and when you become pregnant.

Can PCOS go away with metformin?

Unfortunately, polycystic ovary syndrome is a chronic condition without a known cure. However, the symptoms of PCOS can be managed by medications, including metformin.

Metformin works by reducing insulin resistance, which is a common symptom of PCOS. By improving insulin sensitivity, metformin can help to regulate menstrual cycles, reduce symptoms such as hirsutism (excess hair growth, particularly on the chest and face) and acne, and improve fertility.

(Since metformin has the potential to increase fertility in women with PCOS, it’s important to use effective birth control methods if you’re sexually active and taking it for PCOS but do not wish to become pregnant.)

While metformin can be an effective treatment for managing the symptoms of PCOS, it is important to note that it is not a cure for the condition. Women with PCOS may need to continue taking metformin or other medications to manage their symptoms over the long term. 

Lifestyle changes like eating a healthy, balanced diet and getting regular exercise can also help manage the symptoms of PCOS.

According to the 2020-2025 Dietary Guidelines for Americans, a healthy diet should:

  • Focus on a range of fruits, vegetables, whole grains, and dairy items, preferably those without fat or with low-fat content.
  • Incorporate various proteins like fish, lean meats, poultry, eggs, legumes (including beans and peas), and soy products, along with nuts and seeds.
  • Strive to minimize the consumption of added sugars, salt, saturated and trans fats, as well as cholesterol.
  • Be tailored to meet your daily calorie requirements for maintaining good health.

The current Physical Activity Guidelines for Americans recommends 150 minutes of moderate-intensity physical activity and 2 days of muscle-strengthening activity each week. 

If you have PCOS, it’s important to work with your doctor or medical provider to develop a plan of care that works for your health history, minimizes symptoms, and meets your goals.

What are the benefits of metformin for PCOS? 

To understand how metformin can help people with PCOS, it’s important to understand some of the biological changes that occur with PCOS.

While the underlying cause or “trigger” for PCOS isn’t well understood, researchers do know that PCOS involves a series of interrelated changes occurring between the ovaries, the pancreas, insulin levels, and the body’s sex hormones (among other hormones).

All of these complex hormonal changes cause the ovaries to develop extra follicles or cysts (the “cysts” in “polycystic”) and insulin resistance. Insulin resistance leads to higher blood sugars and taxes the pancreas, as it has to try to produce more insulin to bring the body’s blood sugar down to a normal level.

Metformin works in several different ways at once, many of which can help with the symptoms of PCOS. 

Metformin lowers the amount of sugar produced by the liver, decreases sugar absorption in the intestines, and allows individual cells in the body to consume more sugar and use that sugar more efficiently.

Together, these three effects decrease the amount of sugar (in the form of glucose) circulating in the bloodstream. This allows the body to become more insulin sensitive, which means the pancreas doesn’t need to make as much insulin in the first place.

These changes can lead to more regular menstrual cycles, reduce sex hormone imbalances, and help reduce both acne and hirsutism that occur with PCOS.

Large clinical trials also demonstrate that metformin helps people lose weight they might have gained from PCOS.

Frequently asked questions

What dose of metformin will I be prescribed for PCOS?

Metformin dosages for the treatment of PCOS vary, and a doctor is more likely to start you on a lower dose at first (e.g., 500 milligrams [mg] with a meal) to manage adverse side effects of the drug, like nausea and upset stomach.

Meta-analysis (analysis of data from several clinical trials) has shown that 1,500 mg to 2,550 mg per day is generally sufficient to address the major symptoms of PCOS.

However, as with all prescription drugs, your doctor will evaluate your health goals, history, and any underlying symptoms to determine the appropriate starting dose.

See more in: Metformin Dosage Guide (Min and Max Doses).

Can metformin prevent PCOS?

Studies have not definitively proven any way to prevent PCOS. However, the symptoms of PCOS can be reduced or managed through medications (including metformin) and through living a healthy lifestyle, involving steps such as maintaining a balanced diet and getting enough exercise. 

Does metformin work for everyone with PCOS?

While the drug is generally safe and often effective, metformin unfortunately doesn’t work for everyone with PCOS.

Metformin is highly effective in reducing blood sugar levels for women with PCOS. Most — though not all — women also experience significant improvements in acne and unwanted sex hormone-associated hair growth.

While many women also see their periods become more regular with the use of metformin, only about 40 percent will experience “totally normal” menstruation.

Metformin’s weight loss effects also vary significantly from person to person.

How quickly after taking metformin will I see a change in my PCOS symptoms?

Metformin needs time to build up in the body. Oftentimes, your doctor will start you on a lower dose of the drug to avoid uncomfortable GI side effects.

Most people will see improvements in their blood sugar levels after a few weeks. 

How long does it take metformin to regulate periods?

Long-term studies of metformin’s use for PCOS show that it may take as long as 6 months for the drug to establish regular menstruation.

Final thoughts

While it is not a cure, metformin’s ability to improve symptoms like irregular menstruation, weight gain, and hormonal imbalances makes it a valuable tool in the long-term management of PCOS. 

However, its off-label status for treating PCOS and the potential side effects highlight the importance of a personalized approach under medical supervision. 

Additionally, lifestyle changes remain a cornerstone of managing PCOS, complementing metformin’s effects. Ultimately, the best strategy is a comprehensive, individualized treatment plan that includes both medical and lifestyle approaches for the condition.

Suggested next article: Everything You Need to Know About Metformin.


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