Is Metformin safe during pregnancy?
What the FDA-approved label for Metformin actually states in its Pregnancy Risk Summary — not a secondhand verdict. The decision is one to make with your prescriber.
What the label’s pregnancy summary says
The label's §8.1 Pregnancy Risk Summary states that limited data with metformin in pregnant women are not sufficient to determine a drug-associated risk for major birth defects or miscarriage, and that published post-marketing studies have not reported a clear association between metformin and major birth defects or miscarriage — though those studies cannot rule out risk because of methodological limitations. It stresses that poorly controlled diabetes in pregnancy itself carries substantial maternal and fetal risk (birth defects, stillbirth, preeclampsia, preterm delivery). The label does not tell patients to start or stop the drug; decisions about diabetes treatment in pregnancy should be made with the prescriber.
Frequently asked questions
Is Metformin safe to take during pregnancy?
The honest answer is uncertainty: the label does not have enough pregnancy data to call Metformin safe or unsafe (summary above). That is a "decide with your prescriber" situation, weighing your condition against the unknown, not a green or red light. The one universal rule: do not start or stop a medication in pregnancy without medical advice — an untreated condition can carry its own risk to a pregnancy.
What does the FDA label say about Metformin in pregnancy?
The summary above is transcribed from the label's Pregnancy Risk Summary (§8.1). Since 2015 FDA labels replaced the old A/B/C/D/X letter categories with a narrative that describes what human and animal data actually show, which is what you are reading here — not a single letter grade.
Is Metformin safe while breastfeeding?
That is a separate question the label answers in a different section (§8.2, Lactation), and it does not always match the pregnancy verdict. This page covers pregnancy only. For breastfeeding, ask your prescriber or pharmacist, or check the NIH LactMed database, which summarizes the drug-in-breast-milk evidence.
The questions people actually ask about metformin in pregnancy
Answered by MotherToBaby, the fact sheets written by the Organization of Teratology Information Specialists and published through the NIH. Quoted in full — we do not condense them.
I take metformin. Can it make it harder for me to get pregnant?
Based on the studies reviewed, is it not known if metformin can make it harder to get pregnant. Metformin has been used to treat PCOS, a condition that can make it harder to get pregnant.
Does taking metformin increase the chance of miscarriage?
Miscarriage is common and can occur in any pregnancy for many different reasons. Metformin is not expected to increase the chance for miscarriage. Poorly controlled diabetes in the first trimester of pregnancy can increase the chance of miscarriage.
Does taking metformin increase the chance of birth defects?
Every pregnancy starts out with a 3-5% chance of having a birth defect. This is called the background risk. Use of metformin during pregnancy is not expected to increase the chance of having a baby with a birth defect. Poorly controlled diabetes in the first trimester of pregnancy can increase the chance of having a baby with a birth defect.
Does taking metformin in pregnancy increase the chance of other pregnancy-related problems?
Some studies have suggested people with gestational or type II diabetes who were treated with metformin had smaller babies at the time of delivery than those who were treated with insulin. The children exposed to metformin during pregnancy quickly gained weight after birth. Some studies have shown that children exposed to metformin during pregnancy may have a higher chance of having obesity in childhood. However, other studies did not show a difference in obesity in children of individuals who took metformin in pregnancy compared to people who did not take metformin or those who took insulin.
Does taking metformin in pregnancy affect future behavior or learning for the child?
Taking metformin during pregnancy is not expected to affect future behavior or learning for the child.
Quoted from MotherToBaby Fact Sheets — Metformin, published January 2024. MotherToBaby states its fact sheets should not take the place of medical care and advice from your healthcare providers.
Breastfeeding is a separate question — what LactMed says about metformin
More guides for Metformin
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The pregnancy information is transcribed from the drug’s FDA-approved label (§8.1) and mirrors what the label states — “insufficient data” is never rounded up to “safe.” This is general reference information, not medical advice. Whether to take any medication in pregnancy is a decision for you and your prescriber; do not start or stop a drug on your own, because an untreated condition can also carry risk.