@cgi2099 In the US, the standard process is to do what’s called a “screening” or a “challenge” test as a first step.
You aren’t required to fast or do anything special before. You go into the doctors office, drink the glucola drink, and then after an hour you get a blood draw.
If that number is good, no further tests required.
If your numbers are not good, you then do the 3 hour test where I believe you fast for 12 hours, drink the glucola then get your blood drawn once an hour for three hours.