Usually constipation is nothing more than a minor problem, but it can be a symptom of something more serious. If constipation persists for more than three days, or if you have blood in your stool, see your doctor. Common causes The large intestine removes the water from wastes before they are expelled through the anus. The more time that wastes remain in the large intestine, the more water gets removed. Thus constipation, once started, tends to persist.
Constipation often is the result of diet or lifestyle as much as anything else.
For example, people who do not drink enough fluids or eat enough fruits, vegetables, and whole-grain foods may become constipated from time to time. Also, regularity is very much a matter of habit. If you ignore the urge to have a bowel movement, or if you are frequently too busy to take the time for it, you will disrupt the normal functioning of the bowel. Stools will build up and tend to get drier and harder, making them more difficult to pass. Constipation then becomes more likely.