How fast will miralax (polyethylene glycol) work for constipation?

Quickly: It is not like exlax, but it will start to work usually within 48-72 hours.

Transit time: There is a specific transit time we all have for items that enter our digestive system.They have actually worked it out with tracer systems & can vary from 3-5 days in some to 30 minutes in kids with explosive diarrhea. If you have a normal but constipated system, it may take 3-5 days for the med to work down to the outlet. This is more a wetting agent than laxative but works well when used right.