Anxious about glucose test

Hello mummies, i need advice on the glucose tolerance test ogtt. I had the 1st blood test and drank the drink. However an hour later, after taking my 2nd blood test, i became dizzy and vomitted. I have to redo the test again as I did not make it til my 3rd blood test. Any tips or advice to prevent me from dizziness and vomiting? ): Not sure if it's from the drink or the blood test...