Lactulose (a combination of sugars not readily absorbed by the body) draws water into the bowel where it softens the stool and stimulates the bowels to move. In general, an initial dose produces a bowel movement within 24 to 48 hours. Taken daily thereafter, a bowel movement will usually occur in about four hours. Talk to your doctor before trying lactulose. The inexpensive and over-the-counter product contains the sugar galactose and may affect blood sugar levels. As a result, people with diabetes and those who are galactose intolerant should not use the product.