I am also on metformin, along with glipizide and byette. Although me a1c and blood sugar in general are doing great, I also have a rash.
Mine started before the change to glipizide and the addition of byetta. However, mine seems to be quite different from what I'm reading here. My first issue began more than a year ago with very itchy scrotum. The itching was intense, especially when I stood up and got fresh air to that region. Because I drive a cab in Florida, I just attributed it to everyday jock itch and treated with otc meds, and the itching subsided...some.
I also thought it could have been from laundry detergents etc, but the itchy was localized.
A few months later I started itching in various locations. Just a minor itch here and there, didn't think much about it until one day I was having lunch with some friends and they started asking if I was Ok. Evidently I was constantly scratching various spots. Just minor scratching, but pretty much non stop.
Then I started developing rashes. Primarily on my left hand and arm,, areas that get more sun because I'm a smoker and that arm is out of the window often. The dermatologist checked me out (thankfully as the found and removed a couple non related pre cancer spots) and told me to wear sunblock, that it was most likely a sun reaction because of some medicine.
I treated with antihistamines, anti itch creams and antibiotic creams... the rashes went away. Then a month or so later I developed a small bump in the palm of my hand. Within a week I had sores on the palm and fingers (mostly in areas not prone to sun exposure) a wide spread rash on my calve and a few other locations. ...staph infection!
Several shots and pills later it cleared up. ...mostly. ...but now it's coming back. The dermatologists are perplexed, its not mrsa, most all of the rashes are in area that are not typically covered with clothes only a small portion of the area are constantly exposed to the sun... and the scrotal itching is back. I keep insisting is got to be a reaction to one of the meds I'm on, even though the rash isn't widespread. The weird part is its primarily on the left side. No pain, just rashes and itching.