Hi, I would speak to your GP.
Why? Because he may recognise the rash and know what may cause it.
Because I have an intolerance to lactose and other ingredients in meds, I have to be extremely careful with them.
As a T2 an intolerance to certain sugars comes with the diagnosis.
If you do have a side effect, other meds are available to you, even like me, I take Sitagliptin, to help with my first phase insulin response, it could be the same with you or for your insulin resistance.
Take care.