Key takeaways
- MiraLAX usually takes 1 to 3 days to work, so it’s not the one to grab if you need relief fast.
- Adults take one 17 gram dose a day, stirred into 4 to 8 ounces of any drink. Don’t use it for more than seven days unless a doctor tells you to.
- Gas and bloating are the most common side effects. If you get diarrhea, rectal bleeding, or belly pain that keeps getting worse, stop and call a doctor.
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MiraLAX is a laxative used to treat occasional constipation. It's mild, it doesn't taste like anything, and there's a decent chance one is already in your cabinet. But mild doesn't mean you can take it however you like for as long as you like, so here's how it works and how to use it without causing yourself new problems.
What is MiraLAX?
MiraLAX is an over-the-counter laxative that comes as a powder that you mix into a drink. Its active ingredient is polyethylene glycol 3350, or PEG 3350. You can also find generic versions sold under that name, usually at a lower price.
The powder is unflavored and comes in individual packets or bottles with a measuring cap. Each dose is 17 grams. Bottle sizes include 4.1 oz (7 doses), 8.3 oz (14 doses), and 17.9 oz (30 doses). If you’re looking for the ‘238 gram bottle,’ that’s the 8.3 oz size.
What does MiraLAX do? Is it a laxative?
Yes, it's a laxative. More specifically it's an osmotic laxative, which just means it pulls water into your intestines. More water in the colon makes stool softer and easier to pass, therefore you tend to "go" more often.
What it doesn't do is push on the muscles of your gut the way a stimulant laxative does. That's a big part of why it usually causes less cramping.
People also ask whether it's a stool softener or not. The answer: sort of. It does soften stool, so it gets lumped in with that category, but a true stool softener like Colace (docusate) works differently. MiraLAX is in the osmotic category.
How to Take MiraLAX: dosage and instructions
Taken from the website, below is how you should take MiraLAX:
- Do not take more than directed unless advised by your doctor.
- The bottle top is a measuring cap marked to contain 17 grams of powder when filled to the indicated line (white section in cap).
- Children 16 years of age or under: Ask a doctor.
Adults and children 17 years of age and older:
- Use once a day.
- Fill to top of white section in cap, which is marked to indicate the correct dose (17 g).
- Stir and dissolve in any 4 to 8 ounces of beverage (cold, hot or room temperature), then drink.
- Do not combine with starch-based thickeners used for difficulty swallowing.
- Ensure that the powder is fully dissolved before drinking.
- Do not drink if there are any clumps.
- Do not use for more than seven days.
How long does MiraLAX take to work?
The label says it generally produces a bowel movement in 1 to 3 days. Some people notice something in 24 hours, others need the full three. If you want faster relief, MiraLAX probably isn't the right pick (more on that in the comparisons below).
When is the Best Time to Take MiraLAX
There is not a recommended time of day to take MiraLAX. Begin taking MiraLAX when you experience the first signs of constipation. Continue taking until you experience relief (up to seven days).
Most Common Side Effects
The most common ones are gas and bloating. Some people get nausea, cramps, or loose, watery stools. These tend to be more likely in the first weeks and often settle down.
Does MiraLAX cause gas? It can, yes. It's one of the most common complaints. If it's mild, it usually isn't a reason to quit. If your bloating, cramping or belly pain keeps getting worse, stop taking it and call a doctor. Stop and get medical advice if you notice rectal bleeding. And if you get diarrhea, stop. Diarrhea on a laxative can dry you out fast, so make sure to drink fluids.
MiraLAX vs. other laxatives
MiraLAX vs. Dulcolax
Dulcolax (bisacodyl) is a stimulant laxative and works faster, usually in about 6 to 12 hours. MiraLAX is osmotic and takes more like 1 to 3 days. Faster doesn't mean better, though. Stimulants can cramp more.
MiraLAX vs. Colace
Colace is a stool softener. It makes stool easier to pass but it isn't strong or quick, so it's usually not the pick if you're already backed up and want relief.
MiraLAX vs. Metamucil
Metamucil is psyllium fiber. It bulks up stool, and it's generally the gentlest option for ongoing, day-to-day regularity. It works slower and it needs plenty of water. MiraLAX is more of a treat-the-problem tool.
MiraLAX vs. milk of magnesia
Milk of magnesia is magnesium hydroxide, another osmotic-type laxative, and it tends to work faster than MiraLAX, anywhere from about 30 minutes to a few hours. Because it contains magnesium, people with kidney problems need extra care.