After soaking a metformin tablet in water for 12 hrs in a glass why is it still whole ? I cut it?

You're right. I've been taking Metformin. I've been passing the pill whole!!! I even took a video. The entire pill is whole with a yellow coat around it, and the medication was still there. Nothing had distributed anywhere. It's like my body is rejecting it. On a brighter not.. it's definitely GUT related. I have celiacs disease too. And it literally stops the ability for me to digest properly and absorb nutrients... especially pill form... hope this helps. You're NOT crazy and IT is happening to people. Don't let them tell you it's not AFTER seeing it with your own eyes and experiencing it.

My metformin is the "osmotic" type. It has a tiny pinhead hole on either one or both sides. The contents inside leak out over time, so it's a controlled release version, and then it's said that you do poop out the shell, but I've never seen it.

Sorry but you are wrong. I am not familiar with the exact tablet you are referring to but most probably the acid in the stomach will dissolve the protective coating on the tablet, the tablet then will then either break down or the medicine will now pass through the coating and be absorbed into the bloodstream in the small intestine.