Is metformin safe?

Hi. Is Metformin and Levothoryxin safe during pergnancy? A friend of mine is taking them and she would like to have a second opinion.

[Forum-M.D.-SP]

She should consult her provider. Levothyroxine is pregnancy category A, which means that controlled studies have shown no risk in pregnancy, and that the risk of fetal harm is remote. Metformin is Category B, which means there have been controlled studies in animals showing safety, but no studies in human. Category B drugs are described as follows: 'fetal harm possible but unlikely'. With all medications, one must balance the risk of not taking them with the risk of taking them. For example, the risk of a bad pregnancy outcome due to an underactive thyroid usually outweighs the risk of taking thyroid medicine.