Glucose test ?

I go for mine in 3 weeks , and I’m having high anxiety about it. Just sitting alone for an hour waiting for the process of this test is triggering my Anxiety, I don’t know why. I already have IBS and I’m nervous it’s going to upset my stomach and I’ll have to use the bathroom or even vomit. For those who took it already how did it go ? Is it better to do this test early morning or mid afternoon.