Have never heard of weight GAIN with metformin. That must be one of the more unusual side effects.
Usually it’s a weight loss drug. If only because you stay in the potty...
They put my wife on it to treat a small pituitary tumor and she gained 40 pounds in no time and had memory and energy issues as well.
She got off it and her energy and memory came back but she has battled for years now to drop the weight and can’t.