Taking vitamin c to bowel tolerance is imo not a good idea. One can lose plenty of minerals that way. I use licorice root tea which has very mild laxative properties. i normally drink a cup or two a day, but when I am stopped up, I might drink up to 4 cups. It usually does the job. It also increases my mood. Also be careful about taking too much acidic vitamin c. if you plan to take larger doses of vitamin c, then make sure you are using a buffered variety(Ester c, or calcium or magnesium ascorbate). These buffered vitamin c supplements are also a good source of calcium or magnesium that is well absorbed. Be careful about which form of calcium you take. Calcium carbonate is very constipating and very poorly absorbed. Calcium citrate or calcium ascorbate(calcium with vitamin c) are much better absorbed and not constipating. Msm supplements also help cure constipation. So does certain detoxifying herbs like licorice root, ginger, dandelion, and alfalfa.

The main causes of constipation are not eating enough fiber(vegetables and fruits are best rather than fiber supplements), not drinking enough water, and not getting enough exercise.