Hi
@BaffourKwame and welcome to the forums.
Can I ask what type of diabetes you have?
Do you mean that your gums have been receding, getting smaller?
My understanding is that gum disease is very common in diabetics because we often have higher blood sugars, so we need to be extra careful with our dental hygiene and keep up visits to the dentist.
Googling isn't giving me anything on metformin and gum disease, though. It's not something I had heard of before.
I would suggest you ask your dentist about help with the gum issues. My only suggestion would be to try to keep your blood sugar levels in normal range.