It can be accurate whatever stage you are, if you're pregnant or not. Some ladies get it much sooner if they've had history of diabetes or their family does.
Yes, It will be accurate. According to this app, (I'm Expecting) It says the test can be given 24-28 weeks. But It's usually given around 26-28 weeks.
I had mine at 25 weeks and its just as accurate by this stage. I'm now 35+5 and healthy!! Baby boys great too!
I was 25 weeks when i had mine done, you should be ok. they wouldn't make u go thru wit it if was too soon
I had a 1hr one at 16weeks and them a 3hr one at 32weeks because I switched doctors because I moved