You poor thing, I hope you get better quick. Your body is fighting virus or infection of some sort, so yes, its normal to have higher bg levels as a result.
If I were you I would give the metformin a miss today, have plenty of soothing drinks, eg fruit/herbal teas, or warmed coconut milk with a little sweetener, cinnamon, cocoa powder or ginger added.
Or maybe you can have a light vegetable soup/bouillon, home made would be best, use lots of fresh vegetables.
You have to make sure that you avoid becoming dehydrated, let nature take its course, just relax, rest up, if you dont feel any better by tomorrow contact your GP.