After drinking celery juice you should wait for 15 to 20 minutes before eating anything else.
What I do is drink the celery juice when I wake up in the morning while I have an empty stomach and then I go about my day by taking my shower, getting dressed etc and by that time more than 15 minutes has passed and then I'm ready to eat my normal breakfast.
I also drink another glass of celery juice around 20 minutes before eating dinner.
Drinking Celery Juice in the evening before bedtime can also help you fall asleep faster and get more rest.