The fastest way to relieve constipation depends on how urgently you need results. A rectal option like a glycerin suppository or sodium phosphate enema can produce a bowel movement in as little as 2 to 15 minutes. If you prefer something oral, magnesium citrate typically works within 30 minutes to 6 hours. Here’s a practical breakdown of your options, ranked roughly by speed.
Rectal Options: The Fastest Relief
If you need results within the hour, rectal treatments are your best bet. A sodium phosphate enema is the fastest-acting option available over the counter, often producing a bowel movement within 2 to 5 minutes. Most enemas lead to a bowel movement within 15 minutes, though some types take up to an hour for full effect.
Glycerin suppositories work within 5 to 30 minutes. They soften stool and lubricate the rectal wall, triggering the muscles to push things along. A bisacodyl suppository (the rectal version of the same ingredient found in many oral laxatives) falls in the 15 to 60 minute range. All three are widely available at pharmacies without a prescription.
Oral Options That Work Within Hours
Magnesium citrate is the go-to oral option when you want same-day relief. It draws water into the intestines, softening stool and triggering contractions. Most people have a bowel movement within 30 minutes to 6 hours. It comes as a flavored liquid you drink in one or two doses over the course of a day. The taste is tart but tolerable when chilled.
Stimulant laxatives like bisacodyl and senna (sold under various brand names) take 6 to 12 hours when swallowed as a tablet. They work by activating nerve endings in the smooth muscle of the colon wall, which increases the wave-like contractions that move stool forward. Because of that timeline, many people take them before bed and have a bowel movement the next morning. They’re effective but not “fast” in the way most people searching this phrase are hoping for.
Osmotic laxatives like lactulose and sorbitol liquid take 1 to 3 days to work. They’re better suited for ongoing management than acute relief.
Things You Can Do Right Now Without a Pharmacy
Change Your Sitting Position
The angle of your body on the toilet matters more than most people realize. When you sit upright on a standard toilet, a sling-shaped muscle around your rectum stays partially contracted, creating a roughly 90-degree bend that acts like a kink in a garden hose. When you raise your knees above your hips (by propping your feet on a stool, a stack of books, or even an overturned bucket), that muscle relaxes and the angle opens to about 126 degrees. The kink straightens, and stool passes with significantly less straining. This is one of the simplest changes you can make, and it costs nothing.
Drink Coffee
Coffee stimulates the release of a hormone called gastrin from the stomach lining, which in turn triggers contractions in the colon. This effect can kick in within minutes of your first cup. It doesn’t work for everyone, but for many people it’s a reliable and near-immediate nudge. Both caffeinated and decaf have some effect, though caffeinated coffee tends to be stronger.
Try Prune Juice
Prune juice contains high amounts of sorbitol (a sugar alcohol that pulls water into the intestines), along with dietary fiber and polyphenols. It works through a similar mechanism as osmotic laxatives. A glass of warm prune juice can get things moving for mild constipation, though it’s less predictable and slower than pharmacy options. A Harvard-cited study found that regular prune juice consumption reduced hard stools within three weeks, so it’s also worth keeping in the rotation if constipation is a recurring issue for you.
Quick Comparison by Speed
- Sodium phosphate enema: 2 to 15 minutes
- Glycerin suppository: 5 to 30 minutes
- Bisacodyl suppository: 15 to 60 minutes
- Magnesium citrate (oral): 30 minutes to 6 hours
- Bisacodyl or senna tablet (oral): 6 to 12 hours
- Lactulose or sorbitol liquid (oral): 1 to 3 days
When Constipation Signals Something Serious
Most constipation is uncomfortable but harmless. However, certain symptoms point to a possible fecal impaction or bowel obstruction, which need medical attention rather than over-the-counter laxatives. Watch for sudden constipation with abdominal cramps and a complete inability to pass gas or stool. Blood in the stool, very thin pencil-like stools, or chronic diarrhea that follows a long period of constipation also warrant a call to your doctor. If you’re experiencing cramping with no gas or stool passing at all, do not take a laxative. That combination can indicate an obstruction, and adding a laxative to a blocked system can make things worse.
Preventing the Next Episode
Once you’ve solved the immediate problem, a few daily habits can keep constipation from coming back. Fiber is the cornerstone: most adults need 25 to 30 grams a day but get closer to half that. Beans, lentils, berries, pears, and whole grains are the most efficient sources. Increase fiber gradually, because adding too much at once causes bloating and gas that can make you feel worse before you feel better.
Water matters too, especially if you’re increasing fiber. Fiber absorbs water to add bulk and softness to stool. Without enough fluid, extra fiber can actually slow things down. Physical activity, even a daily 20-minute walk, stimulates the natural contractions of the colon. People who are sedentary are significantly more likely to develop chronic constipation than those who move regularly. If you use the toilet-stool trick described above, keep it by the toilet permanently. The positioning benefit applies every time, not just during constipation episodes.