Chiropractors work, on average, about 40 hours per week, although longer hours are not uncommon. Solo practitioners set their own hours but may work evenings or weekends to accommodate patients. Like other health care practitioners, chiropractors in a group practice will sometimes be on call or treat patients of other chiropractors in the group.
Source: Bureau of Labor Statistics, U.S. Department of Labor, Occupational Outlook Handbook, 2008-09 Edition