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Last updated on March 31, 2017

The Best Laxative

Gentle help when you’re feeling blocked
The 30-Second Review

The best laxative should be effective, fast-acting, and as gentle as possible on your body. After speaking with doctors and reading through peer-reviewed medical research, we narrowed a starting pool of 62 products down to three top picks — best-selling products with few side effects when taken as directed.

Best for Fast-Acting Relief

A chalky liquid that’s unpalatable but typically produces a bowel movement within six hours. No serious side effects, as long as you don't take it for more than a week.

Best for Sensitive Stomachs

A powder that’s tasteless once dissolved. Takes 1-3 days to work, but a low risk of side effects.

Most Convenient

Phillips' Laxative Caplets

The same active ingredient as Phillips’ Milk of Magnesia, but in pill form.

The Best Laxatives

If you’re constipated, you’re not alone. The American College of Gastroenterology reports “at least 2.5 million doctor visits for constipation in the USA each year.” Diet, exercise, getting enough sleep, and drinking plenty of water are the best medicine when it comes to treating constipation since all drugs, even gentle laxatives, can have side effects. But sometimes you just need fast-acting relief.

Who shouldn’t take an OTC laxative? If you have kidney problems, or are pregnant or breastfeeding, consult with your doctor before taking an over-the-counter laxative.

To get back to “regular” as quickly as possible, we recommend Phillips’ Genuine Milk of Magnesia. This product is a hyperosmotic laxative that works by drawing water into the intestine, encouraging bowel movements and making stool easier to pass. Phillips’ Genuine Milk of Magnesia typically produces bowel movement within six hours (possibly as soon as 30 minutes), and it’s generally held to be safe as long as you’re not taking it on a regular basis. The one drawback is actually having to swallow it: It’s a viscous liquid that left an extremely chalky, unpleasant residue in our mouths.

For those with sensitive stomachs, we’d recommend MiraLAX Laxative Unflavored instead. MiraLAX is also a hyperosmotic laxative, but it can take up to three days to kick in. However, its active ingredient, polyethylene glycol, carries a lower risk of side-effects than the magnesium used by Phillips’ (which can lead to diarrhea and cramping if used long enough). MiraLAX is also notably more palatable: It comes as a white powder that can be mixed into any beverage (hot or cold) and, apart from a slight mineral undertone, tastes like nothing.

Phillips' Laxative Caplets are also worth a mention. Like their liquid counterpart, the caplets use magnesium to encourage bowel movement, and according to Phillips’ website, they typically work within six hours. But because this product is marketed as a dietary supplement (for reasons we explore below), its efficacy hasn’t technically been verified by the FDA. That said, Phillips’ is a respected brand, and all our research suggested the caplets’ active ingredient will work just fine. If you want a more convenient option than measuring liquid or mixing powder, we’d suggest giving them a shot.

Our Picks for the Best Laxative

Best for Fast Relief

Phillips’ Genuine Milk of Magnesia Original is a hyperosmotic laxative, which means it draws water into the stool and intestine to encourage bowel movement and make stool easier to pass. And it works quickly: according to its packaging, the product “usually produces bowel movement ½ to 6 hours.”

While prolonged use of a magnesium laxative can lead to an electrolyte imbalance (in turn leading to diarrhea and stomach cramps), Phillips’ Genuine Milk of Magnesia Original is gentle enough when used as directed. Its active ingredient, magnesium hydroxide, is recommended by the American Gastroentrological Association as a good preliminary treatment option for constipation. Side effects are rare, but can include flushed skin, and drowsiness. Because all laxatives can lead to loss of fluids, it’s also important to drink plenty of water to avoid dehydration.

The main drawback is that Phillips’ Genuine Milk of Magnesia Original tastes pretty disgusting. It’s a thin, slightly viscous liquid that you pour into a measuring cap before swallowing. (The consistency put us in mind of laundry softener.) While it has no discernable odor or taste, we found the texture extremely unpleasant: it left a chalky residue in in our mouths that was hard to wash out. We even refrigerated the bottle for six hours to see if it would become any more palatable, and while this made the liquid a bit easier to swallow, it didn’t help with the aftertaste.

One does is 2-4 tablespoons, or one to two gulps, and the product is meant to be taken once daily for no more than seven days.

Best for Sensitive Stomachs

MiraLAX Laxative Unflavored Takes longer to kick in, but tasteless and with fewer side effects.

Like Phillips’, MiraLAX is a hyperosmotic laxative, although it relies on polyethlene glycol rather than magnesium to draw water into the intestine. MiraLAX states that it “generally produces a bowel movement in 1 to 3 days,” versus the six hours advertised by Phillips’ Milk of Magnesia. So if you need relief as soon as possible, Phillips’ is a better bet.

But according to Dr. Leila Kia, Assistant Professor of Medicine at Northwestern University, MiraLAX Laxative is more likely to be recommended by doctors than magnesium-based products like Phillips’. “I typically recommend a trial of soluble fiber (along with increased water intake). If this is ineffective, my first line laxative is polyethylene glycol 3350 (or Miralax),” she told us. “It is safe, effective, and can be titrated up or down to get the desired effect. I start with 17 grams of powder dissolved in 8 ounces of water, once daily.”

Mukherjee echoed Kia’s preference, explaining that MiraLAX is often preferred by doctors because of the risk of electrolyte disturbance that comes with prolonged use of magnesium-based products. So if you’re looking for a laxative that’s as safe and gentle as possible, MiraLAX is it. As with milk of magnesia, side effects are minimal but can include bloating, dizziness, and sweating.

Unlike Phillips’ Genuine Milk of Magnesia, MiraLAX comes in a salt-like powder you can dissolve in your beverage of choice.

MiraLAX is a popular pick Doctors aren’t the only ones who love MiraLAX. Consumer Reports named polyethylene glycol (MiraLAX’s generic form) a top pick in its 2008 laxative review — and it turns out that the laxative landscape hasn’t changed much since then.

Miralax is also a lot more palatable than Phillips’. MiraLAX Laxative Unflavored is a white powder with a consistency similar to table salt. The label says you can add it to any beverage, hot or cold, and we had no trouble dissolving it in a cup of cold tapwater. You will need to stir, otherwise the product clumps up, but the powder dissolved entirely after 20 seconds of stirring.

The powder itself has a very faint chemical smell that reminded us of Elmer’s Glue, but we didn’t find it too off-putting — and we couldn’t smell anything at all after it had been dissolved. There was also no noticeable taste, apart from faint mineral undertones. Unlike Phillips’ Genuine Milk of Magnesia, we felt it would be pretty easy to disguise MiraLAX in the beverage of your choosing.

Most Convenient

Phillips’ Laxative Caplets A pill with the same active ingredient as Phillips' Milk of Magnesia

Phillips’ Laxative Caplets are also a magnesium-based drug, so they come with the same caveat about prolonged use as the brand’s liquid medication. But if you don’t want the hassle of measuring out doses (or choking down milk of magnesia), pills may be preferable. Note that they’re uncoated, so we’d suggest swallowing quickly — otherwise they’ll start to dissolve, leaving behind that same chalky milk of magnesia taste. A daily serving is 2-4 pills; each is roughly the size and shape of a Tylenol tablet.

In its FAQs, Phillips’ says the caplets typically start working in “one-half to six hours,” the same time frame as its milk of magnesia. But it’s worth noting that, unlike our other two picks, Phillips’ Laxative Caplets are classified as a dietary supplement rather than a drug. This doesn’t mean they aren’t effective, just that they contain a few extra binding ingredients that cause the product to fall outside the FDA’s very narrow definition of “laxative drug.” The upshot is that the caplets’ efficacy claims haven’t been vetted by the FDA. We weren’t overly concerned by this — Phillips’ has a solid reputation, and the caplets have a 4.5 star average on Amazon — but if you don’t want to take the gamble, we’d suggest one of our other top picks.

Did You Know?

To ward off constipation, develop good bowel hygiene.

Dr. Neil Mukherjee told us that the best long-term treatment for constipation is developing good bowel hygiene.

“The most common reason [for] constipation [is] a lack of dietary fiber, hydration, and exercise. To achieve the best the body can do, we need to have a good bowel hygiene. That would include a scheduled exercise and sleep pattern. It also means [having] regular nutritious meals with fiber and adequate hydration,” Dr. Mukherjee said. “If these things can be controlled early on, most of the problems of long-term constipation can be alleviated.”

Of course, sometimes we just need a little extra help. But how do you know when you’ve hit that point? “I would recommend to start taking laxatives when bowel habits change or the usual bowel habits are forcing one to make changes,” Dr. Mukherjee said. “The usual problems are forceful straining, painful hard stools, and feeling blocked up or bloated.”

A rubric can help you determine if you're constipated.

Drs. Mukherjee and Kia both gave a rubric for assessing constipation. If you meet two or more of the following criteria, it might be time to reassess your dietary habits:

  • Fewer than three bowel movements per week.
  • Passage of lumpy or hard stools at least 25% of the time.
  • Presence of straining at least 25% of the time.
  • Sensation of incomplete evacuation at least 25% of the time.
  • Sensation of blockage at least 25% of the time.
  • Need to use manual maneuvers to facilitate a bowel movement at least 25% of the time.

Sometimes a laxative isn't enough.

“If someone has tried over-the-counter laxatives without success, it’s a good idea to see a doctor to discuss other possible treatments or further testing. If someone experiences any of the following symptoms, they should also consult a doctor: rectal bleeding, abdominal pain, waking up at night with the urge to have a bowel movement, weight loss, sudden change in type and frequency of bowel movements, or family history of colon cancer,” Dr. Kia said.

The Bottom Line

Best for Fast-Acting Relief

Phillips’ Genuine Milk of Magnesia Original Usually produces a bowel movement within six hours.

Hyperosmotic laxatives like MiraLAX and Phillips’ Genuine Milk of Magnesia are generally safer for short-term constipation relief than lubricant or stimulant laxatives, and more effective than stool softeners. But as with any drug, consult your doctor if you have questions or notice side effects — and remember to drink lots of water. Consider dietary changes or fiber supplements, as well, to help ensure that constipation doesn’t become an ongoing issue.