In May 2020, the Food and Drug Administration (FDA) recommended that some makers of metformin extended-release remove some of their tablets from the United States market. This is because an unacceptable level of a probable carcinogen (cancer-causing agent) was found in some extended-release metformin tablets. If you currently take this drug, call your healthcare provider. They will advise whether you should continue to take your medication or if you need a new prescription.

Metformin is a drug for lowering blood sugar in type 2 diabetes. Research suggests that it may be safe for pregnant individuals to use, but people should speak first with a doctor.

Metformin is a medication that helps lower blood sugar due to type 2 diabetes. Research suggests that as well as lowering blood sugar, metformin improves insulin sensitivity and reduces fat distribution in the body.

This article explores metformin use during and after pregnancy and in relation to fertility. It also discusses side effects, dosage, and alternatives to metformin. Finally, it answers some frequently asked questions.

A note about sex and gender

Sex and gender exist on spectrums. This article will use the terms “male,” “female,” or both to refer to sex assigned at birth. Click here to learn more.

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Some people have concerns about using metformin during and after pregnancy because it crosses the placenta. This means that when a pregnant person takes metformin, so does their fetus.

Research from 2018 stated that there is no evidence that there is an increase in pregnancy loss or congenital anomalies. This is regardless of whether a person takes metformin before pregnancy or even during pregnancy to term. However, further research may be necessary.

Metformin and gestational diabetes

A 2020 randomized control trial notes that pregnant women who took metformin to treat type 2 diabetes gained less weight compared with the placebo group.

The same trial also noted that babies born to the women receiving metformin treatment had less fat, including lower mean fat mass and lower birth weight.

However, there was also a higher proportion of babies in the metformin group that were smaller than expected for their gestational age. The researchers noted that more research is necessary to determine the long-term consequences of these effects.

Doctors may prescribe metformin to people with polycystic ovary syndrome (PCOS) to help with insulin resistance relating to this condition.

According to the Centers for Disease Control and Prevention (CDC), people with PCOS are often insulin resistant. They are also at a higher risk of developing type 2 diabetes, particularly if they have more weight.

PCOS can cause missed periods and infrequent ovulation, which may lead to infertility or difficulty in conceiving.

According to a 2021 systematic review, women with PCOS or gestational diabetes who took metformin experienced lower gestational weight gain compared with the placebo group.

The risks and side effects of metformin may be relatively low when a person uses it as a doctor recommends. However, some people will experience mild side effects. The most common side effects of metformin include:

For pregnant people, these symptoms may make the feeling of morning sickness worse. A doctor may prescribe the lowest effective dose to help reduce or prevent side effects with metformin.

Metformin rarely causes hypoglycemia, which has the following symptoms:

Metformin may also cause more serious complications in rare cases, such as lactic acidosis. Symptoms of this condition vary greatly but may include:

If a person feels they have any serious symptoms or signs of lactic acidosis, they should contact an emergency medical team immediately.

The dosage of metformin for people with type 2 diabetes varies. A doctor will choose a dosage according to a person’s medical history, insulin sensitivity levels, and sensitivity to side effects.

A doctor may also prescribe metformin for pregnant people who take insulin for type 2 diabetes to help with symptoms that develop during pregnancy.

Metformin dosage for people with PCOS also varies according to their reaction to the medication.

To minimize side effects, doctors start an individual on very low doses and gradually increase these until their symptoms improve.

Pregnant people with gestational diabetes or type 2 diabetes may take metformin during their pregnancy with instructions from a healthcare professional.

However, metformin does not have approval for use by pregnant people in the treatment of type 2 diabetes. A doctor may decide to prescribe it to a person who cannot tolerate insulin or due to other individual circumstances.

Below are some of the most common questions and answers about metformin and pregnancy.

Does metformin help with gestational diabetes?

Health experts do not recommend metformin as an alternative to insulin for treating gestational diabetes. However, it may have off-label use for someone who cannot tolerate insulin, upon the decision of a doctor and the individual.

When does a person start metformin in gestational diabetes?

A doctor may prescribe metformin to a person with gestational diabetes as soon as they receive a diagnosis.

An individual may start on an initial dose of 500 milligrams once or twice a day. A doctor may adjust this dose depending on the severity of gestational diabetes.

Why do some pregnant people get gestational diabetes?

A person develops gestational diabetes when their body cannot make enough insulin during pregnancy or when their body has become more resistant to the insulin it makes. Insulin is a hormone that transports glucose, or sugar, into the cells, which use it as energy.

A person’s body will release hormones during pregnancy that result in changes such as weight gain. This results in the body reacting less effectively to insulin, which people call insulin resistance. This means that the body requires more insulin than usual.

What are the risks of having diabetes while being pregnant?

Risks to a pregnant person with gestational diabetes include:

Risks to the fetus during gestational diabetes include:

What should I avoid while taking metformin?

A person should inform their doctor about any medications they are taking, as some can interact with metformin.

Medications that may increase the risk of lactic acidosis include:

Some drugs that may cause hypoglycemia when a person takes them alongside metformin include:

A doctor may also recommend that a person:

Should a person stop taking metformin during pregnancy?

Individuals should stop taking metformin if they are pregnant unless they have discussed continuing the medication with their doctor.

A doctor will monitor a person taking this medication to ensure they are not experiencing unwanted side effects.

If a healthcare professional feels that someone should not be taking metformin during pregnancy, they may offer an alternative.

Research suggests that metformin has a low risk of complications during pregnancy. However, further research may be necessary.

Some studies suggest that the drug may even have benefits for pregnant people and their fetuses following appropriate use.

Doctors will carefully manage metformin dosages depending on each person’s medical history. An individual should speak with their doctor for further advice about their concerns.