To fully clear or clean out your colon of toxins for health it can take around 4 weeks to 8 weeks of using colon cleanse pills or just naturally cleansing your colon.
If you're needing to cleanse your colon for a medical test such as a colonoscopy then it should take only 16 to 18 hours to have your colon cleansed enough for the colonoscopy.
But if you're cleansing your colon for the health benefits then it can take awhile and you should continue to cleanse your colon.
After 1 to 2 months though your colon should be almost free of toxins but then again your colon will always have more toxins in it.
So it's important to keep cleansing your colon often to improve your health and prevent colon cancer.