Metformin while pregnant: what we know
Metformin while pregnant can be appropriate in some cases. Here is what labeling and guidelines say, plus risks and monitoring.
Key facts
- Answer a few health questions online. A licensed clinician reviews them. If approved, it ships to your door.
- Adults 18 or older. A licensed clinician reviews your health history and decides whether treatment is appropriate for you. Availability depends on the state you live in.
If you are taking metformin and find out you are pregnant, it is normal to want a direct safety answer. The best next step is to review why you are taking it, your pregnancy timing, and your health history with a prenatal clinician. This page explains what metformin labeling and major guidelines say about metformin while pregnant, what risks to watch for, and when to seek urgent care. Vitals Vault also offers PocketMD, an AI health companion you can use to organize questions for your next visit.
- Metformin while pregnant may be used for some people, but it should be an individualized clinician decision.
- Metformin crosses the placenta, so benefits and uncertainties should be discussed early in pregnancy.
- Important risks include lactic acidosis (rare) and low vitamin B12 with long-term use.
- If you have diabetes, avoiding high blood sugar in pregnancy is a key safety goal.
Can you take metformin while pregnant?
Why it is prescribed
Metformin is FDA-approved for type 2 diabetes. In pregnancy it may be continued or started for diabetes-related reasons, and it is also used off-label in some settings such as polycystic ovary syndrome (PCOS), depending on clinician judgment and guideline context.
What makes pregnancy different
Metformin can reach the fetus because it crosses the placenta. That does not automatically mean it is unsafe, but it does mean you should weigh potential benefits against uncertainties and discuss monitoring with your prenatal care team.
Do not self-stop suddenly
If you are using metformin for blood sugar control, stopping without a plan can worsen hyperglycemia, which is a known pregnancy risk. Contact your prescribing clinician promptly to decide whether to continue, adjust, or switch therapy.
Details that matter for safety
- FDA-approved use
- Type 2 diabetes mellitus (not specifically pregnancy).
- Placental transfer
- Metformin crosses the placenta, so fetal exposure occurs.
- Most important rare risk
- Lactic acidosis is rare but serious; risk rises with kidney impairment and certain acute illnesses.
- Long-term monitoring issue
- Long-term metformin use can be associated with vitamin B12 deficiency.
What the label says in pregnancy
Metformin labeling summarizes available human pregnancy data and notes that metformin crosses the placenta. Your clinician may use this information along with your glucose control, kidney function, and pregnancy risks to decide whether metformin remains appropriate.
If you take it for diabetes
For people with diabetes, the main safety goal is avoiding sustained high blood sugar during pregnancy, which is linked to adverse outcomes. Some guidelines allow metformin in selected situations, but insulin is often used when tighter control is needed or when metformin is not a good fit.
If you take it for PCOS
Metformin is commonly used off-label in PCOS. Whether to continue it after conception varies, because evidence and guideline recommendations differ by goal, such as metabolic health versus pregnancy outcomes. A prenatal clinician can help you decide based on your history.
Common side effects
The most common metformin side effects are gastrointestinal, such as diarrhea, nausea, and abdominal discomfort. Taking it with meals and using extended-release formulations may improve tolerability for some people, but any change should be clinician-guided in pregnancy.
Serious side effects to know
Lactic acidosis is a rare but life-threatening emergency associated with metformin, especially with significant kidney disease, dehydration, severe infection, or low oxygen states. Get urgent care for severe weakness, unusual muscle pain, trouble breathing, increasing sleepiness, or persistent vomiting.
Interactions and temporary holds
The label warns about iodinated contrast imaging procedures, which can affect kidney function and raise lactic acidosis risk. If you need a contrast study during pregnancy, your clinicians should coordinate whether metformin should be paused and when it can be restarted.
When to call your clinician or seek urgent care
Call promptly if pregnant
If you are newly pregnant or planning pregnancy, contact the clinician who prescribes your metformin and your prenatal clinician. You will usually review why you take metformin, your current blood sugar plan (if applicable), and whether any monitoring or medication changes are needed.
Urgent care symptoms
Seek urgent care if you have symptoms concerning for lactic acidosis, such as severe weakness, trouble breathing, unusual muscle pain, increasing sleepiness, or persistent vomiting. Also seek urgent care for severe dehydration or inability to keep fluids down.
Low blood sugar concerns
Metformin alone is less likely to cause hypoglycemia, but risk can increase if it is combined with insulin or certain other diabetes medicines. If you have shakiness, sweating, confusion, or fainting, follow your pregnancy diabetes plan and contact your care team.
Kidney or liver problems
Tell your clinician if you have a history of kidney disease, liver disease, or conditions that can reduce oxygen delivery, because these can raise metformin risks. Pregnancy can change lab values and fluid balance, so your clinician may adjust monitoring.
Practical tips for your next visit
Bring your full med list
Include supplements and any diabetes medicines, not just metformin.
Ask about the goal
Clarify whether the goal is glucose control, PCOS symptoms, or another reason.
Review kidney function
Ask when your kidney function was last checked and what it means for metformin.
Discuss GI side effects
Nausea and diarrhea can overlap with pregnancy symptoms, so plan ahead.
Plan for imaging
If a contrast scan is needed, ask how metformin should be managed.
Frequently Asked Questions
Is metformin while pregnant safe?
Metformin while pregnant may be appropriate for some people, but safety depends on why you take it and your health history. The FDA label notes metformin crosses the placenta, so your clinician should weigh benefits and uncertainties for your situation.
Does metformin cross the placenta?
Yes. The metformin label notes that metformin crosses the placenta, which means the fetus can be exposed. That is why pregnancy decisions are usually individualized and monitored by a prenatal clinician.
What are the most serious risks of metformin in pregnancy?
The most serious labeled risk is lactic acidosis, which is rare but life-threatening and more likely with kidney impairment or severe illness. Seek urgent care for severe weakness, trouble breathing, unusual muscle pain, increasing sleepiness, or persistent vomiting.
Can metformin cause miscarriage or birth defects?
Human pregnancy data are summarized in the FDA labeling, and clinicians interpret them alongside your condition and alternatives. If you are concerned about miscarriage or birth defects, discuss your specific risk factors and medication plan with your prenatal clinician.
If I am pregnant and on metformin, what should I ask my clinician?
Ask what the goal of metformin is in your pregnancy plan and whether insulin or other options are preferred for your situation. Also ask about kidney function monitoring and what to do if you get dehydrated, develop a severe infection, or need a contrast imaging study.