(HealthDay News) -- Constipation can mean passing fewer-than-normal stools during a week, or passing stools that are dry and hard, or difficult to pass.

The National Digestive Diseases Information Clearinghouse offers these possible causes of constipation:

• Changes in your exercise routine, dietary habits or travel schedule.
• Not going to the bathroom when you have the urge to produce a bowel movement.
• Being under significant stress.
• Lack of fiber or fluids in the diet.
• Taking vitamin supplements, especially iron, calcium or some pain-relieving medications.
• Medical conditions, including pregnancy, digestive problems, diabetes or thyroid problems.