Metformin side effects

Hi everyone. I’ve started taking Metformin this week and I can’t work out whether I’m just tired or whether I’m experiencing side effects.

I’ve been feeling really tired. So much so that I could easily sleep during the day. Concentrating on work has been difficult - I guess you could call it brain fog. My colleagues are considerate so it’s not a huge problem but I just wondered if others have experienced this. I’m sure it will pass eventually but it’s a little irritating.