Hey, I’ve done it twice 😅 So no eating or drinking since midnight. I’d advise to come at 7:30 straight because you take a number and then they do bloods based on what number you are. They’ll take bloods and give you a drink afterwards that u have to drink. Then they’ll take bloods 1 hour later and then third time will be after 2 hours. They will also give u a voucher for tea and toast downstairs once you had your bloods taken 3 times. So the whole test can take 2,5-3 hours in total.
I was in the Rotunda but maybe it's a similar process? I had to fast beforehand and then was in there for 2-3 hours. Blood test on arrival and then a glucose drink to have and they took my bloods at intervals throughout the time, I think it was twice more