A stool softener is one type of laxative, not an alternative to one. "Laxative" covers every product that helps you have a bowel movement, and fiber supplements are laxatives too (the bulk-forming kind)[1].
In the stool softener vs. laxative choice, the evidence favors fiber first, then an osmotic laxative such as MiraLAX. Docusate stool softeners have the weakest trial support[2][3].
The right pick also depends on what your constipation looks like: hard, dry stools, too few bowel movements, or soft stool that is still hard to push out. Below is a side-by-side comparison, a decision table by symptom, the evidence for each class, and how long each takes to work.
Get medical help promptly if constipation comes with blood in your stool or bleeding from your rectum, constant belly pain, vomiting or inability to pass gas, fever, or weight loss you did not try for. These need a clinician, not another laxative[4].
What is the difference between a stool softener and a laxative?
A stool softener (docusate, sold as Colace and Surfak) is a mild laxative that softens stool so it is easier to pass. MedlinePlus describes it as a short-term option for people who should avoid straining, such as those with hemorrhoids or some heart conditions[5]. Every other laxative class works differently:
- Bulk-forming (fiber): psyllium absorbs liquid in the intestines, swells and forms a bulky stool that is easier to pass[6]. Citrucel and FiberCon are other fiber supplements[1].
- Osmotic: polyethylene glycol 3350 (MiraLAX), magnesium and lactulose keep water in the stool, which softens it and increases bowel movements[7].
- Stimulant: senna and bisacodyl (Dulcolax tablets) increase the activity of the intestines to trigger a bowel movement[8][9].
- Lubricant: mineral oil coats the stool[1].
What category does MiraLAX fall under?
MiraLAX is an osmotic laxative. It softens stool, but it is not a stool softener in the drug-class sense[7]. The 2023 guideline from the American Gastroenterological Association and American College of Gastroenterology (AGA-ACG) grouped docusate with osmotic and surfactant laxatives when it searched the evidence[2].
Stool softener vs. laxative vs. fiber: side-by-side
| Fiber (bulk-forming) | Stool softener | Osmotic laxative | Stimulant laxative | |
|---|---|---|---|---|
| Examples | Psyllium (Metamucil), methylcellulose (Citrucel) | Docusate (Colace) | Polyethylene glycol 3350 (MiraLAX), magnesium oxide, lactulose | Senna (Senokot), bisacodyl (Dulcolax) |
| How it works | Psyllium absorbs liquid and swells into bulky stool[6] | Softens stool[5] | Keeps water in the stool[7] | Increases intestinal activity[8] |
| How fast | Clearest gains in trials lasting 4 weeks or more[10] | 1 to 3 days of regular use[5] | PEG: 2 to 4 days[7] | 6 to 12 hours[8][9] |
| AGA-ACG 2023 rating | Conditional, low certainty | No recommendation made | PEG strong; magnesium oxide and lactulose conditional | Bisacodyl strong (short term or rescue); senna conditional[2] |
| Common side effects | Gas[10] | Cramps, nausea[5] | Bloating, gas, cramping, loose stool[7] | Cramping, abdominal pain, diarrhea[2] |
Which one should you choose for your type of constipation?
Match the product to the problem. The AGA-ACG panel suggests fiber as a first step, especially if you eat little of it, and polyethylene glycol (PEG) when fiber is not enough or alongside it[2]. Stimulants are for occasional or rescue use, and NIDDK advises using them only if constipation is severe or other treatments have not worked[1].
| What you notice | Reasonable first choice | Why |
|---|---|---|
| Hard, dry, lumpy stools; low-fiber diet | Fiber supplement, with plenty of fluid | Fiber improved stool consistency and response rates in a 16-trial meta-analysis[10] |
| Hard stools that persist despite fiber | Osmotic laxative such as PEG | Strongest over-the-counter evidence; fiber can be continued with it[2] |
| No bowel movement for several days and you want relief soon | Short course of a stimulant laxative | Works within 6 to 12 hours[8]; backed for short-term or rescue use[2] |
| Soft stool that is still hard to push out, week after week | See a clinician | Pelvic floor disorders can delay emptying[4] |
| Need to avoid straining (hemorrhoids, after some surgeries) | Stool softener, or the plan your care team gave you | This is the labeled use of docusate[5] |
| Constipation from opioids or other medicines | Ask the prescriber | Docusate's evidence for opioid constipation is weak[11] |
| Pregnant | Ask your obstetric clinician | Very few trials exist in pregnancy[12] |
If you are not sure which stool type you have, the Bristol stool chart gives a common vocabulary. Medicines such as iron supplements, opioid pain relievers, some antidepressants and aluminum or calcium antacids can cause constipation, so it is worth asking whether one of yours is involved[4]. Do not stop or change a prescribed medicine without talking to the prescriber[1].
What does the evidence say about each option?
Fiber: the usual first step
Fiber supplements work, but slowly and at a real dose. A 2022 meta-analysis of 16 randomized trials (1,251 adults) found that 66% responded to fiber versus 41% on control[10].
Benefits appeared mainly at doses above 10 g a day, and stool frequency improved mainly in trials lasting at least 4 weeks[10]. Psyllium and pectin drove most of the effect. The AGA-ACG panel likewise concluded that, among fiber supplements, only psyllium appears effective[2].
Take each dose of psyllium with at least 8 ounces (240 mL) of liquid, and keep digoxin, aspirin and nitrofurantoin at least 3 hours apart from it[6]. Expect some extra gas at first[10]. For dosing and product forms, see our psyllium husk page. Food sources are covered in high-fiber foods for constipation and prune juice for constipation.
Stool softeners: gentle, but weak in trials
Docusate is widely used, yet controlled trials show little benefit. In a 1998 double-blind trial of 170 adults with chronic constipation, psyllium (5.1 g twice daily) raised stool water content by 2.33%. Docusate (100 mg twice daily) raised it by 0.01%[3].
Psyllium also produced more stool output (359.9 vs. 271.9 g a week)[3]. The trial was funded by Procter & Gamble, which makes Metamucil.
In 74 hospice patients, adding docusate to senna did no better than adding a placebo over 10 days[13]. A 2021 review of docusate for opioid-induced constipation found that most guidelines endorsing it cited no primary evidence[11]. The 2023 AGA-ACG guideline searched for docusate trials, noted a paucity of data, and made no recommendation for it[2].
That does not make docusate harmful. Its main side effects are cramps and nausea, and it interacts with mineral oil[5]. It is simply a weak choice if your goal is more frequent bowel movements.
What is the best osmotic laxative to take?
Among osmotic laxatives, polyethylene glycol 3350 is the best-supported product you can buy without a prescription. In the AGA-ACG analysis, PEG added about 2.9 complete bowel movements a week over placebo. About 312 more people per 1,000 met the responder definition[2]. A Cochrane review of 10 trials found PEG beat lactulose on stool frequency, stool form, abdominal pain and the need for extra products[14].
Magnesium oxide is an option too. In a 34-woman trial, 70.6% improved on magnesium oxide (0.5 g three times daily) versus 25.0% on placebo[15]. People with reduced kidney function should avoid it because magnesium can build up[2].
Stimulant laxatives: fast, best for short courses
Stimulants act quickly and work well in trials. In a 4-week trial of 368 adults, bisacodyl 10 mg daily raised complete bowel movements from 1.1 to 5.2 a week, compared with 1.9 on placebo[16]. Sodium picosulfate, a related drug, gave similar results, and about half of users lowered their dose during the trial[17]. In a 90-person trial, 69.2% improved on senna (1.0 g daily) and 68.3% on magnesium oxide, against 11.7% on placebo[18].
The trade-off is cramping and abdominal pain, and the senna dose studied was higher than people usually take[2]. MedlinePlus advises older adults not to take senna long term, and says to stop and call a doctor if you notice rectal bleeding[8].
MiraLAX vs. Metamucil vs. Colace: what are the differences?
They do different jobs, so "better" depends on the problem. Metamucil (psyllium) is a fiber supplement suited to daily use and low-fiber diets[2]. MiraLAX (PEG 3350) is an osmotic laxative with the stronger trial record, often the next step when fiber is not enough[2][14]. Colace (docusate) is a stool softener for short-term use when straining should be avoided, with little proof that it increases bowel movements[5][3].
Is it better to take MiraLAX or Metamucil?
Neither is better for everyone: start with Metamucil if your diet is low in fiber, and move to or add MiraLAX if stools stay hard[2]. In a head-to-head trial, psyllium beat docusate on stool water, stool output and, by week 2, bowel movement frequency[3]. We found no trial comparing MiraLAX directly with Metamucil. The guideline notes the two can be combined[2].
Is Metamucil a good choice for constipation?
For many people it is a sensible first step. Psyllium is the only fiber supplement that appeared effective in the AGA-ACG review, and it suits people who eat little fiber[2]. Results depend on dose and patience: trials showed benefit mainly above 10 g a day and over at least 4 weeks[10].
What is the downside to taking Metamucil?
The main downsides are gas, slow onset and the need for fluid. Flatulence was more common with fiber than with control in trials[10]. Each dose needs at least 8 ounces (240 mL) of liquid, and it can interfere with digoxin, aspirin and nitrofurantoin if taken within 3 hours of them[6]. MedlinePlus also asks you to tell your doctor first if you have had an intestinal blockage or have trouble swallowing[6].
Can you take a stool softener and a laxative together?
Yes, combinations are common and some are sold as one pill. Docusate plus sennosides is the formula in products such as Peri-Colace and Senokot S[5]. Psyllium plus senna is sold as Perdiem[6]. The AGA-ACG guideline describes stimulant laxatives as a rescue option alongside other treatments, and fiber can be used together with PEG[2].
The combination with the least support is the classic softener-plus-stimulant pairing. In hospice patients, the docusate added nothing measurable to senna[13]. Check with a pharmacist before stacking products, especially if you take other medicines.
Is it safe to take a laxative or stool softener every day?
For some types, daily use under medical guidance appears reasonable. For others, the label sets a one-week limit.
Is it safe to take MiraLAX for a long time?
In the guideline's review, the response to PEG held up over 6 months. The panel judged longer-term senna and magnesium oxide use probably appropriate, while noting long-term safety data are limited[2].
The consumer labels are more cautious. MedlinePlus says PEG is usually taken for up to 2 weeks and "may be habit-forming"[7]. Senna and bisacodyl should not be used for more than a week without a doctor[8][9]. Docusate and psyllium carry the same one-week label limit unless a doctor directs otherwise[5][6].
What is the best thing you can take every day for constipation?
For most adults the guideline starting point is fiber, with PEG added or substituted when fiber alone is not enough[2]. Among over-the-counter options, PEG has a strong recommendation and a 6-month durability record, while stimulants are framed as short-term or rescue treatment[2]. Which is safest for you depends on your kidneys, heart, other medicines and pregnancy status, so check with a pharmacist or doctor.
If you can no longer have a bowel movement without a laxative, NIDDK advises asking your doctor how to taper off slowly. Your colon should start moving stool normally again over time[1]. Needing a laxative most days is itself a reason to get chronic constipation properly assessed.
How do fiber laxatives affect your gut microbiome?
Fiber can also change which bacteria thrive in your gut. In two small 7-day trials, psyllium shifted the gut bacteria of 16 constipated patients more than those of healthy volunteers[19]. Genera that rose included Faecalibacterium (see Faecalibacterium prausnitzii), Lachnospira and Veillonella. Levels of acetate and propionate also changed.
Rises in three butyrate-producing genera (Lachnospira, Roseburia and Faecalibacterium) tracked with wetter stools[19]. These were short, small trials, so they show association, not proof that the bacteria cause the laxative effect. Lactulose is covered in our prebiotics section; as a laxative, its common side effects are dose-dependent bloating and flatulence[2]. Evidence on probiotics is covered separately in probiotics for constipation.
When to see a doctor
See a doctor if constipation does not improve with self-care, or if you have a family history of colon or rectal cancer[4]. Seek care right away if constipation comes with[4]:
- bleeding from the rectum or blood in the stool
- constant pain in the abdomen
- inability to pass gas, or vomiting
- fever or lower back pain
- weight loss you were not trying for
Also call a doctor if stools are still hard after a week of a stool softener, or if a stimulant laxative causes rectal bleeding[5][8]. Tell your doctor before using PEG if you have had a bowel obstruction[7].
This article is for general educational purposes and is not medical advice. Doses mentioned are those used in studies or listed by MedlinePlus, not personal recommendations. Talk to a qualified healthcare professional or pharmacist before starting or combining laxatives, particularly if you are pregnant, older, have kidney or heart disease, take prescription medication, or have constipation that keeps coming back.
Frequently Asked Questions
How long does a stool softener take to work?
Docusate stool softeners usually need 1 to 3 days of regular use before they take effect, according to MedlinePlus. That is slower than a stimulant laxative such as senna or bisacodyl, which normally produces a bowel movement within 6 to 12 hours. MedlinePlus advises not taking a stool softener for more than 1 week unless a doctor directs it, and calling a doctor if stools are still hard after a week.
Is MiraLAX a stool softener or a laxative?
MiraLAX (polyethylene glycol 3350) is an osmotic laxative. It keeps water in the stool, which both softens it and increases how often you go, so it is often described as softening stool. It is not a stool softener in the drug-class sense: that term usually means docusate (Colace). In the 2023 AGA-ACG guideline, polyethylene glycol received a strong recommendation for chronic idiopathic constipation, while docusate received none.
Can MiraLAX cause gas and bloating?
Yes. MedlinePlus lists nausea, bloating, cramping and gas as possible side effects of polyethylene glycol 3350, and the 2023 AGA-ACG guideline adds abdominal distension and loose stool. Diarrhea was more common with polyethylene glycol than placebo in the trials the guideline reviewed. Fiber supplements cause gas too: in a 2022 meta-analysis, flatulence was higher with fiber than with control.
How do you tell if it is constipation or a blockage?
Ordinary constipation means infrequent, hard or difficult stools while you still pass gas and feel otherwise well. NIDDK advises seeing a doctor right away if constipation comes with constant abdominal pain, inability to pass gas, vomiting, fever, blood in the stool or unexplained weight loss. MedlinePlus also says to tell your doctor before using polyethylene glycol if you have symptoms of a bowel obstruction, such as vomiting and stomach pain or bloating.
Is Dulcolax or Metamucil safe to take while pregnant?
The evidence on laxatives in pregnancy is thin. A 2015 Cochrane review found only two usable trials (180 women). Fiber supplements increased stool frequency by about 2 bowel movements a week compared with no treatment. Stimulant laxatives (the class that includes Dulcolax tablets) worked better than bulk-forming ones such as Metamucil but caused more abdominal discomfort. No trials tested stool softeners or osmotic laxatives in pregnancy. Ask your obstetric clinician or pharmacist before taking any laxative while pregnant.
Should I use a stool softener after surgery?
Stool softeners are mainly meant for short-term use by people who need to avoid straining, such as after some surgeries or with hemorrhoids or certain heart conditions, according to MedlinePlus. Trials show docusate has little measurable effect on its own, though. If you were sent home with a specific bowel plan after surgery, follow it, and ask the surgical team before adding or swapping products.
What is the downside of taking MiraLAX?
The common downsides are bloating, gas, cramping, nausea and loose stools, according to MedlinePlus and the 2023 AGA-ACG guideline. It is also slower than a stimulant, often taking 2 to 4 days to produce a bowel movement. MedlinePlus says it is usually taken for up to 2 weeks and may be habit-forming, so longer use should be agreed with a doctor. Tell your doctor first if you have ever had a bowel obstruction or have vomiting with stomach pain or bloating.
References
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- Mori S, Tomita T, Fujimura K, et al.. A Randomized Double-blind Placebo-controlled Trial on the Effect of Magnesium Oxide in Patients With Chronic Constipation. Journal of Neurogastroenterology and Motility. 2019;25(4):563-575. doi:10.5056/jnm18194 ↩
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