The best overall laxative for most people with constipation is polyethylene glycol (sold as MiraLAX and store-brand equivalents). It’s the only over-the-counter option that received a strong recommendation for ongoing use from the American College of Gastroenterology, and it works for both adults and children. That said, different situations call for different laxatives, and what works best depends on whether you need relief tonight, a gentle daily option, or something safe for pregnancy.
Why Polyethylene Glycol Is the Top Choice
Polyethylene glycol (PEG) is an osmotic laxative, meaning it pulls water into your colon to soften stool and make it easier to pass. It’s tasteless, mixes into any beverage, and doesn’t cause the cramping that stimulant laxatives often do. Clinical guidelines rank it above fiber supplements, senna, and magnesium-based products because the evidence behind it is stronger and more consistent.
For children, PEG is also the first-line treatment. Pediatric guidelines recommend a starting dose based on body weight, and caregivers can adjust up or down to keep stools soft without causing diarrhea. It typically produces a bowel movement within one to three days, so it’s not instant relief, but it’s reliable for daily management.
How Each Laxative Type Works
Bulk-Forming Laxatives (Fiber Supplements)
Products like psyllium husk (Metamucil) add soluble fiber to your stool. The fiber absorbs water, making stool larger and softer, which triggers your colon to push things along. They’re the closest thing to a “natural” laxative and work well for mild, occasional constipation. The catch: you need to drink a full 8-ounce glass of water with every dose, and taking fiber without enough liquid can actually make things worse or, in rare cases, cause a blockage. Expect results in 12 to 72 hours.
In a head-to-head comparison, psyllium significantly increased stool water content within three days, bringing hard stool into the normal range and sustaining that effect over two weeks. It’s a solid daily option if you’re willing to be consistent with it.
Osmotic Laxatives
This category includes PEG, lactulose, and magnesium-based products like milk of magnesia and magnesium citrate. They all draw water into the colon, but they differ in strength and speed. PEG is gentle and works within one to three days. Magnesium citrate is much more aggressive, often producing a bowel movement within one to three hours. It’s useful when you need fast results but isn’t meant for regular use, especially if you have kidney problems, since your body may struggle to clear the extra magnesium.
Stimulant Laxatives
Senna (Senokot) and bisacodyl (Dulcolax) work by activating the nerves in your colon wall, forcing the muscles to contract and move stool through. They typically work within 6 to 12 hours when taken by mouth. A systematic review in the American Journal of Gastroenterology found good evidence supporting senna and moderate evidence for bisacodyl. Current guidelines give bisacodyl a strong recommendation for short-term use (under four weeks) or as a rescue option when gentler laxatives aren’t enough.
The old worry about stimulant laxatives causing “lazy bowel,” where your colon becomes dependent on them, has been largely overstated. But they do cause more cramping and urgency than osmotic or bulk-forming options, which is why they’re better suited as occasional backup rather than a daily go-to.
Stool Softeners
Docusate sodium (Colace) is probably the most widely recommended stool softener, but the evidence behind it is surprisingly weak. A comprehensive review of seven randomized, placebo-controlled studies found that docusate performed no better than a placebo at softening stool. An eighth study measured stool water content directly: docusate had no significant effect, with stool staying in the “hard” range throughout two weeks of treatment. Psyllium, by comparison, moved stool water content into the normal range within three days. Despite its popularity, docusate is one of the least effective options on the shelf.
Picking the Right Laxative for Your Situation
If you’re dealing with chronic, recurring constipation, PEG is the best starting point. It’s effective, well-tolerated, and safe for long-term use. If you prefer a more natural approach, a daily fiber supplement like psyllium is a reasonable alternative, though the evidence supporting it is slightly weaker.
If you haven’t had a bowel movement in several days and need faster results, a stimulant laxative like bisacodyl or senna will work within 6 to 12 hours. For truly urgent situations, magnesium citrate can produce results in as little as one hour, but it’s powerful and can cause significant cramping and loose stools.
If you’re pregnant, bulk-forming laxatives are the safest first step since they aren’t absorbed by the body. Stool softeners like docusate are also generally considered safe during pregnancy, even though their effectiveness is questionable. Osmotic options like milk of magnesia and lactulose, as well as stimulant laxatives like bisacodyl, are also considered acceptable during pregnancy according to the Mayo Clinic.
When Over-the-Counter Options Aren’t Enough
Most people find relief with one of the options above, but gastroenterologists note that many patients who end up in their offices have already tried multiple OTC laxatives along with diet changes without success. For chronic constipation that doesn’t respond to over-the-counter treatments, prescription medications are available that work through different mechanisms than standard laxatives. These are strongly recommended by clinical guidelines when OTC options fail, so persistent constipation is worth bringing up with your doctor rather than cycling through the same products indefinitely.
A Practical Starting Approach
For most adults, a reasonable strategy looks like this: start with PEG daily, give it a few days to work, and use a stimulant laxative as a backup if you go more than three days without a bowel movement. At the same time, increase your water and fiber intake from food. If you’ve been doing this consistently for a few weeks without improvement, that’s a signal to explore other options rather than just increasing doses.
For children, PEG remains the first choice, with lactulose or milk of magnesia as alternatives. Prune juice (which contains sorbitol, a natural osmotic agent) can be helpful for infants. In all age groups, the goal is soft stool every one to two days without cramping or diarrhea.