The best over-the-counter laxative for most people is polyethylene glycol 3350, sold as MiraLAX. It’s the only OTC laxative that received a strong recommendation for ongoing use from the joint American College of Gastroenterology and American Gastroenterological Association clinical guidelines. But “best” depends on your situation: how quickly you need relief, whether constipation is occasional or chronic, and how your body responds. Here’s what each type does and when it makes sense.
Why PEG 3350 Is the Top-Ranked Option
Polyethylene glycol 3350 (MiraLAX) is an osmotic laxative, meaning it pulls water into your colon to soften stool and make it easier to pass. The standard dose is 17 grams of powder mixed into 4 to 8 ounces of liquid, taken once daily. In clinical trials, people taking PEG 3350 had nearly double the rate of complete, comfortable bowel movements compared to placebo: 34% of all bowel movements were complete without straining or hard stool, versus 18% with placebo.
It typically produces a bowel movement within one to three days, not hours. That slower pace is actually a feature. It means you’re less likely to get cramping or urgency. You shouldn’t take it for more than seven consecutive days without a doctor’s guidance, but clinicians frequently recommend it for longer-term management of chronic constipation under supervision.
Fiber Supplements: Best for Prevention
Bulk-forming laxatives like psyllium (Metamucil) work by absorbing water and forming a gel in your digestive tract. This makes stool bigger, softer, and easier to move. Unlike most other fiber supplements, psyllium doesn’t ferment in the gut, which means less gas and bloating. That’s a meaningful advantage: many people quit fiber supplements because of discomfort, and psyllium avoids the main cause of it.
Psyllium is the only fiber supplement with enough clinical evidence for the American College of Gastroenterology to recommend it for chronic constipation. Methylcellulose (Citrucel) and calcium polycarbophil (FiberCon) don’t have the same body of research behind them. Psyllium also has an unusual dual effect. It softens hard stool in constipation but also firms up loose stool in diarrhea, essentially normalizing stool consistency in both directions.
The tradeoff is speed. Fiber supplements take two to three days to reach full effect, sometimes longer. They’re better suited for keeping you regular over time than for solving a problem right now. Start with a low dose and increase gradually to give your gut time to adjust.
Stimulant Laxatives: Fastest Relief
If you need results within hours, stimulant laxatives like bisacodyl (Dulcolax) or senna (Senokot) are the most effective option. They work by activating the nerves that control your colon muscles, forcing contractions that push stool through. Most people have a bowel movement within 6 to 12 hours of an oral dose.
Clinical guidelines give bisacodyl and sodium picosulfate a strong recommendation for short-term use (under four weeks) or as rescue therapy when gentler options haven’t worked. Senna received a conditional recommendation, meaning it’s reasonable to try but the evidence is less robust.
The concern with stimulant laxatives has always been whether long-term use damages the colon. A 2024 review in Therapeutic Advances in Gastroenterology found that at recommended doses, the risk of serious side effects like dehydration or electrolyte problems is negligible. The scary findings you may have read about, such as nerve damage in the colon or structural changes, come from studies involving extreme misuse: patients taking 18 times the recommended dose for over a decade, or roughly half of long-term users in one study showing colon dilation and loss of normal tissue patterns. At normal doses for short stretches, they’re considered safe. Still, they’re best used as a backup rather than a daily habit.
Stool Softeners: Weaker Than You’d Think
Docusate sodium (Colace) is one of the most commonly purchased laxatives, but the evidence behind it is surprisingly thin. It works by lowering surface tension in stool so that water and fats can penetrate it more easily. In theory, this should soften stool. In practice, systematic reviews have found that docusate is no more effective than placebo at increasing stool frequency, softening stool, or reducing constipation symptoms.
If you’ve been taking Colace without much improvement, that’s consistent with what the research shows. Switching to psyllium or PEG 3350 is likely to produce noticeably better results.
Magnesium and Saline Laxatives
Magnesium-based products like milk of magnesia (magnesium hydroxide) and magnesium citrate are osmotic laxatives that draw water into the bowel. They tend to work faster than PEG 3350, often within 30 minutes to 6 hours, making them a middle ground between the gentleness of osmotic laxatives and the speed of stimulants.
The catch is that magnesium is absorbed into your bloodstream to some degree, and your kidneys have to clear it. People with kidney problems can accumulate dangerously high magnesium levels. Magnesium citrate also interacts with several common medications, including certain antibiotics, heart medications like digoxin, osteoporosis drugs, and vitamin D supplements. If you take any of these, PEG 3350 is a safer osmotic choice.
Lubricant Laxatives
Mineral oil coats the inside of the colon, preventing water absorption from stool and creating a slippery passage. It works, but it’s fallen out of favor for a few reasons. It can interfere with the absorption of fat-soluble vitamins (A, D, E, K) over time. More importantly, if even a small amount is accidentally inhaled, particularly while lying down or by someone with swallowing difficulties, it can cause a serious condition called lipoid pneumonia. It should not be given to children under 3.
How to Choose the Right One
Your best starting point depends on your timeline and pattern:
- Chronic or recurring constipation: Start with psyllium fiber daily, and add PEG 3350 if fiber alone isn’t enough. This combination addresses the problem from two angles and is well-supported for ongoing use.
- Occasional constipation that needs relief soon: PEG 3350 for a gentle approach within one to three days, or bisacodyl if you want results the same day.
- Already tried Colace without results: Switch to PEG 3350 or psyllium. The evidence strongly favors both over docusate.
Drinking enough water matters with every type of laxative, but it’s especially important with fiber supplements and osmotic laxatives. Both work by pulling water into your stool, and if you’re dehydrated, they’ll be less effective and may cause discomfort.
Laxatives for Children
PEG 3350 is considered the first-line treatment for constipation in children, both for initial relief and ongoing management. If PEG isn’t available or tolerated, lactulose (another osmotic laxative) is the recommended alternative. Stimulant laxatives and mineral oil are second-line options, reserved for children who don’t respond to osmotic treatment. Senna can cause diaper rash, blistering, and skin peeling in young children, so it requires extra caution in that age group.