What happens if I fail my glucose testing??

I got a call yesterday saying I have to come in for the 3 hour glucose testing because I failed the screening 1 hour test 😔. this has happen to me with my first too but I ended up doing fine, they also told me I have anemia which really makes sense to why I have been feeling so weak and bad. I know there's not alot of symptoms to know if I have gestational diabetes but I think I'm making myself paranoid. I feel so sick all the time/dizzy/fatigue and like I can't breathe. it feels really different then my first pregnancy so I'm not sure if something is up. I'll be 30 weeks on Sundays. has anyone failed the 3 hour test? If so what happens?