Different types of laxatives take different amounts of time to take effect, but the fastest is the stimulant laxative, which takes between 30 minutes and seven hours to work. The suppository form of the stimulant laxative is the type that yields results within a half-hour, according to Everyday Health.
The slowest type of laxative is the bulk-forming type. It works by drawing water into the stool to soften and enlarge it, making it easier to pass. It is also considered the safest type, and it is the only one that is appropriate to use daily. Saline laxatives also draw fluid in, but they use phosphate or magnesium, both of which can pose risks for people with kidney failure, notes Everyday Health.