Hi Coco!
It depends what insulin you take. If it's seperate bolus and basal, I'd take the basal as usual but don't bolu until you eat after your blood test. If I'm at the hospital for the blood test, I take my breakfast with me, have the blood test, go to the hospital cafe buy a cup of tea, jab the bolus and eat my breakfast.
If you're on a daily intermediate acting insulin e.g. Insuman basal or HumalinI, I'd take it as usual and do as above.
If you're on twice-daily mixed insulin, that would be a bit trickier and I can't help with that.
The Metformin I'd leave until you eat your breakfast - I don't think it really matters what time of day you take that as long as you take it with food.
I hope it goes well tomorrow.
Take care
Smidge