ok, if it’s M3, then that is a mix of fast and slow insulins. They’re mixed in a set proportion so you can’t increase one part of the mix without increasing the other part because the two insulins are mixed together. Sometimes the proportions of the mix don’t suit people because they need a different balance of slow and fast insulin.
I’m Type 1 so don’t know very much at all about Mounjaro. Could it be that you’ve been started on a small dose of Mounjaro which will be gradually increased? That might account for the high sugars. You could phone your nurse and ask for advice, telling them about your high sugars.
The only other thing you could do is look at the amount of carbs you’re eating but you’d have to proceed very cautiously and slowly in reducing them as you don’t want to risk hypos, so I think it would be best to give your nurse a call.