It depends, you can take one with eack 8oz of water, and that seems to keep urine collered continusly, or 1 dose of 400%-1000% of the daily recomended dosage. That should color your urine for 3-4 voids about 45-60 minutes after taking them. Best advice I can give is to do a practice run and see how your system handles it.
Hope that helps. N2