Blood Glucose Test

Hi. My wife is 27weeks. We did our Blood Glucose test tdy. Didn't go so well as needed to fast 12hrs priors. After reaching KKH and took 1st blood test had to wait 1hr. She ended up vomiting and almost faint. Is this test compulsory?? Any ladies go thru this as well?? Any advice pls. As she's reschedule to do it again next week. #firstbaby #1stimemom #pleasehelp #pregnancy #advicepls