What are some things you wish you knew before starting Metformin?

I just got my first prescription of metformin (500mg). I’m really nervous to start taking it. The doctor was not very helpful and didn’t explain much. He at first wasn’t even going to prescribe it as an option until my boyfriend asked about it. I got the typical diet and exercise advice despite me telling him I’m already meticulously on that. Regardless- what are some things you wish you knew before starting Metformin?

Does it deplete any nutrients? Does it affect the progestin only pill? Are there any major side effects other than nausea I should know about?

Please, any information would be so helpful. Thank you.