The most effective first step for chronic constipation is an over-the-counter osmotic laxative called polyethylene glycol (sold as MiraLAX and generics), which is the only OTC option that received a strong recommendation for long-term use in the joint American College of Gastroenterology and American Gastroenterological Association clinical guidelines. But it’s far from the only option, and what works best depends on what’s actually causing your constipation. Here’s a practical breakdown of everything available, from fiber supplements to prescription medications.
Fiber Supplements: The Usual Starting Point
Fiber supplements are bulk-forming laxatives. They add soluble fiber to your stool, which draws water in and makes it bigger and softer. The increased size triggers your colon to contract and push things along. They typically take 12 hours to three days to produce a bowel movement, so they’re not a quick fix. Psyllium husk (sold as Metamucil) is the best-studied fiber supplement for constipation and received a conditional recommendation in the ACG/AGA guidelines.
The catch with fiber is that it can actually make you feel worse if you don’t drink enough water alongside it. Without adequate fluid, the extra bulk just sits there, causing bloating and discomfort. Aim for at least 48 ounces of water daily when increasing your fiber intake, and ramp up slowly over a week or two rather than jumping to a full dose on day one.
Osmotic Laxatives: The Strongest OTC Evidence
Osmotic laxatives work by pulling water into your colon from surrounding tissues, softening stool so it passes more easily. Polyethylene glycol 3350 (PEG) stands out because it’s the only over-the-counter treatment that gastroenterology guidelines strongly recommend for ongoing, daily use in chronic constipation. It’s tasteless, mixes into any beverage, and generally takes one to three days to work.
A common concern is whether taking PEG every day is actually safe. A study at Nationwide Children’s Hospital measured blood levels of potentially harmful compounds in children taking daily PEG 3350 for at least two weeks and found no sustained elevation compared to children not taking the laxative. The study was small, though, and researchers noted it couldn’t rule out rare adverse effects in all populations. Still, it remains the go-to for gastroenterologists managing long-term constipation.
Magnesium-based options are another form of osmotic laxative. Magnesium citrate and magnesium oxide both draw water into the intestines. Pills typically come in 400 or 500 mg doses, and you should not exceed 1,500 mg per day. One important caveat: if you have kidney disease, magnesium supplements can be dangerous because your kidneys may not clear the excess, leading to a rare but serious buildup in the blood.
Stimulant Laxatives: Fast but Not for Daily Use
Stimulant laxatives like bisacodyl (Dulcolax) and senna activate the nerves controlling your colon muscles, forcing contractions that move stool through. They work faster than most options, typically within 6 to 12 hours, which makes them useful when you need more immediate relief.
The guidelines strongly recommend bisacodyl for short-term use (under four weeks) or as “rescue therapy” for those days when nothing else is working. Senna received a conditional recommendation. These aren’t ideal as your primary daily treatment, but they have a clear role as a backup option alongside a gentler daily regimen.
Stool Softeners: Popular but Limited
Stool softeners like docusate (Colace) increase the water and fat your stool absorbs, making it softer. They take 12 hours to three days to work. Despite being one of the most commonly recommended OTC options, stool softeners have weaker evidence behind them than osmotic or bulk-forming laxatives. Many people find they aren’t enough on their own for true chronic constipation, though they can help as part of a combination approach.
Prescription Options When OTC Isn’t Enough
If you’ve genuinely tried over-the-counter options for several weeks without adequate relief, prescription medications are the next step. Three drugs received strong recommendations in clinical guidelines, all approved for chronic idiopathic constipation (the type with no identifiable underlying cause).
Linaclotide (Linzess) and plecanatide (Trulance) both work by increasing fluid secretion into the intestines, making stool easier to pass. They’re also approved for irritable bowel syndrome with constipation, so if your constipation comes with significant cramping and bloating, these may pull double duty. Prucalopride (Motegrity) takes a different approach, enhancing the natural wave-like contractions of your colon to keep things moving. All three are taken daily and are meant for people who didn’t get results from OTC treatments.
When Laxatives Don’t Work at All
If you’ve cycled through multiple laxatives without meaningful improvement, the problem may not be slow transit through your colon. It may be a coordination issue with your pelvic floor muscles. A condition called dyssynergic defecation occurs when the muscles that should relax during a bowel movement instead tighten or fail to relax properly. It’s surprisingly common in people labeled with “refractory constipation,” and no amount of stool softening will fix it because the exit mechanism itself isn’t working correctly.
A doctor can screen for this with a physical exam that has about 75% sensitivity and 87% specificity, sometimes followed by a balloon expulsion test that pushes accuracy even higher. The most effective treatment isn’t a medication at all. It’s biofeedback therapy, a form of pelvic floor rehabilitation where you retrain the muscles to coordinate properly. Studies have shown biofeedback to be superior to laxatives in patients with this condition, with results that last long after therapy ends. If you feel like you need to strain constantly, feel a sense of blockage, or can never fully empty, this is worth investigating.
A Practical Approach to Trying Treatments
A reasonable sequence looks like this: start with a fiber supplement plus adequate water, give it two to three weeks, and if that’s not enough, add or switch to daily polyethylene glycol. Keep a stimulant laxative on hand for breakthrough episodes. If several weeks of consistent OTC use doesn’t produce regular, comfortable bowel movements, talk to your doctor about prescription options or testing for pelvic floor dysfunction.
Red flags that warrant a prompt medical visit include rectal bleeding or blood in your stool, black-colored stools, unintentional weight loss, persistent stomach pain, unusual changes in stool shape or color, or symptoms lasting longer than three weeks without improvement. These can signal something beyond simple constipation that needs evaluation.