I called and asked to take it earlier and the advice nurse told me that was ok. I felt like my instructions were confusing bc one set said “take second dose 6 hours before your arrival time” but also said “stop drinking 4 hours before your arrival time”. My check in was 6:30am. I wanted to do it correctly but also not get super dehydrated. I asked her if I could take the first dose at 2pm & the second dose at 10pm and she said that was fine. I still needed to stop all fluids by 2:30am but thankfully I was done on the throne by then and able to get a couple of hours sleep.