There is no best time of day to take a laxative in order to end constipation, according to doctors. Since not all laxatives work the same way, when you take one depends on how quickly you want it to work.
The safest laxative is bulk-forming, which works slowly and stimulates the colon naturally. Saline laxatives take a bit less time to work, since they draw additional fluid to the large intestine. This extra fluid helps flush out the colon. Oral stimulant laxatives take about seven hours to work, while suppositories, which you insert into your rectum, should work within about 30 minutes. Stool softeners, mineral oil and lubricant laxatives also can work in concert with an oral laxative to help end constipation.