Is it normal that metformin has significantly affected my husband's weight?

Yes, this is normal and it could have happened. There is scientific evidence that people who take metformin experience (sometimes significant) weight loss. This is because metformin affects appetite, reduces glucose absorption in the gut and improves the body's sensitivity to insulin, which ultimately leads to weight loss. If this is a cause for concern for your husband - please consult your doctor, it may be possible to change the therapy to another one that will not affect his body weight in such a significant way.

The availability of Formetic in pharmacies in Polish can be found here:

https://www.gdziepolek.pl/produkty/31006/formetic-tabletki-powlekane/apteki

I encourage you to read:

https://www.gdziepolek.pl/kategorie/leki-na-cukrzyce