How long does it take for metformin to regulate periods?

In this article:

• What does metformin do for PCOS?
• Metformin dosage for PCOS
• How long does it take for metformin to work for PCOS?
• Bottom line

In this article

• What does metformin do for PCOS?
• Metformin dosage for PCOS
• How long does it take for metformin to work for PCOS?
• Bottom line

Metformin is a prescription medication used to help people with Type 2 diabetes decreasetheir blood sugar levels. It’s a member of the biguanide class of medications and is sometimes sold under the brand name Riomet.

Although metformin is only approved for the treatment of Type 2 diabetes, it has several off-label uses, including in the treatment of polycystic ovarian syndrome (PCOS). Because PCOS is associated with insulin resistance, taking metformin when you have this condition can help you regulate your menstrual cycles. However, it’s not an immediate fix. Here’s what to expect if you’re taking metformin to regulate your periods.

What does metformin do for PCOS?

Women with PCOS experience a range of different symptoms, including heavy menstrual bleeding, excessive hair growth (on the face or chin), and weight gain causing obesity. Having anovulatory cycles (where your body doesn’t release an egg to be fertilized) is extremely common. In fact, more than 90% of women with anovulatory cycles being treated for infertility have PCOS, according to an article published in Diabetes Spectrum in 2015.

According to G. Thomas Ruiz, MD, OB-GYN at MemorialCare Orange Coast Medical Center in Fountain Valley, California, the underlying cause of PCOS-related anovulation is insulin resistance, which leads to an excess amount of insulin in the bloodstream. “Metformin can counteract this effect by decreasing insulin resistance and allowing more insulin to be absorbed by your cells,” he explains.

“Metformin helps lower blood sugar in three ways: by decreasing the production of glucose in your liver, improving your insulin sensitivity, and reducing the amount of glucose absorbed in your intestines,” says Kecia Gaither, MD, OB-GYN and director of perinatal services and maternal-fetal medicine at NYC Health + Hospitals/Lincoln in the Bronx, New York.

How does this benefit people with PCOS, specifically? Less insulin sensitivity helps reduce hyperandrogenism—the excessive release of male hormones that can trigger menstrual irregularities—as well as restore ovarian function and promote more regular ovulation and menstruation, according to Dr. Gaither.   

“If you’re trying to conceive, metformin can also improve the effectiveness of certain ovulatory drugs,” adds Dr. Ruiz. A study from 2017 suggests that metformin may increase the chances of pregnancy when combined with specialized ovulation-inducing gonadotropins like follicle-stimulating hormone (FSH).

Metformin dosage for PCOS

Both Drs. Gaither and Ruiz say the typical starting dosage of metformin for PCOS is 500 milligrams (mg) once or twice per day. From there, your healthcare provider may have you slowly titrate, or increase, your dose as needed. Dr. Gaither says this increase typically maxes out at around 2,000 to 2,500 mg daily, divided into multiple doses.

“Your healthcare provider may also prescribe a single dose of extended-release metformin, which releases a steady amount of the medication over the course of 24 hours,” says Dr. Ruiz. 

How long does it take for metformin to work for PCOS? 

Most women will need to be patient as it often takes several months to see if metformin normalizes their periods, though the timeline is different for everyone. Dr. Gaither says it varies from a few months to six months or more depending on the individual, with factors like the severity of insulin resistance and lifestyle changes like diet and exercise playing a role in how long it takes to see improvements to menstrual regularity.

The other important thing to keep in mind is that metformin doesn’t help all women with PCOS regulate their periods: “It can be hit or miss, though it certainly helps about 25–50% of people taking it,” Dr. Ruiz says.

If metformin addresses the root cause of anovulation—insulin resistance—then why doesn’t it treat the majority of anovulation in people with PCOS? Dr. Ruiz says the reason is that many people with the condition need a two-pronged treatment approach, which not only regulates their insulin but also their hormones. “In order to correct hormonal imbalances, you may need to take progesterone therapy or birth control in addition to metformin.”

There’s also the fact that diet and exercise play a role in regulating your menstrual cycle, especially if you have PCOS.  

“Metformin isn’t a weight loss medication, but if you use it and are more attentive to making some lifestyle changes, you are likely to lose weight, and that can help regulate your periods as well,” Dr. Ruiz says.

Bottom line

PCOS is closely associated with insulin resistance, but taking metformin can improve the way your body makes and absorbs glucose. This leads to better insulin sensitivity and, in some women, more regular menstrual cycles after a few months on the medication. However, metformin doesn’t regulate periods for everyone taking it, and other factors—like hormonal imbalances and your lifestyle—can affect whether or not it works and how long it takes to improve your cycle.

If you have questions about regulating your menstrual cycle with metformin, talk to your healthcare provider. Dr. Ruiz says everyone with PCOS should seek the assistance of their primary care physician, an OB-GYN, or an endocrinologist since the majority of women with the condition are insulin-resistant, and lowering blood sugar levels should be part of their treatment goals. Menstrual irregularities may be a symptom signaling the need for close management of weight and blood sugars.