March 31, 2026 Pregnancy & Medication Safety

Is Metformin Safe During Pregnancy?

Medically reviewed by Andre Stone | MD, University of Pittsburgh School of Medicine on August 25th, 2026.

Metformin may be used during pregnancy for some women with type 2 diabetes or gestational diabetes. Insulin is generally the preferred medication during pregnancy, but metformin can be an alternative after discussing its benefits, limitations, and uncertainties with a clinician. Available studies have not shown metformin to increase the overall risk of major birth defects, but study designs and comparison groups vary. Metformin crosses the placenta, and evidence about some long-term effects in exposed children is still limited. However, evidence about some long-term effects in exposed children is still limited. Metformin may cause less maternal weight gain than insulin in some patients, but the best treatment depends on blood sugar levels, medical history, and pregnancy-specific considerations. However, some women may need to switch to insulin if metformin alone doesn't adequately control blood sugar levels.