What is MiraLAX and How Does It Work?
MiraLAX is an over-the-counter (OTC) osmotic laxative used to treat occasional constipation in adults and children 17 years and older [1.2.2]. Its active ingredient is polyethylene glycol 3350 (PEG 3350) [1.4.4]. Unlike other types of laxatives, MiraLAX works naturally with the water in your body to relieve constipation [1.4.1].
The mechanism of action is straightforward: when you take MiraLAX, it travels through your digestive system and attracts water into the colon [1.4.3]. This process accomplishes two things: it softens the stool and increases the frequency of bowel movements, making them easier to pass [1.4.1, 1.4.4]. MiraLAX typically produces a bowel movement within 1 to 3 days [1.2.3].
Can MiraLAX Cause Diarrhea?
Yes, diarrhea or loose, watery stools are among the most common side effects of taking MiraLAX [1.2.1, 1.3.4]. The very mechanism that makes it effective at relieving constipation—drawing water into the bowels—can sometimes work too well, resulting in stools that are too loose. This is more likely to occur under certain circumstances:
- Taking more than the recommended dose: Using more than the standard 17-gram dose once per day can significantly increase your risk of side effects like diarrhea and dehydration [1.2.2, 1.2.3].
- Individual sensitivity: Some individuals may be more sensitive to the effects of MiraLAX.
- Age: Older adults (ages 65 and older) have a higher risk of developing diarrhea when using MiraLAX [1.2.1, 1.2.2].
Symptoms of an overdose of polyethylene glycol 3350 can include severe diarrhea, thirst, and confusion [1.5.1, 1.5.2].
Proper Usage and Dosage
To minimize the risk of side effects like diarrhea, it is crucial to use MiraLAX correctly. The standard adult dose is one capful of powder (17 grams) dissolved in 4 to 8 ounces of any beverage (such as water, juice, or coffee) and taken once daily [1.9.3, 1.9.4]. The powder should be stirred until it is completely dissolved before drinking [1.5.3]. It is intended for short-term use, typically for up to seven days, unless otherwise directed by a healthcare professional [1.3.1].
If you experience loose stools, you may need to reduce the dosage or stop taking it for a couple of days before restarting at a lower dose [1.2.1, 1.9.4].
Comparison of Laxative Types
MiraLAX is just one of several types of laxatives available. Understanding the differences can help you make an informed choice for your needs [1.4.2].
| Laxative Type | How it Works | Common Examples | Onset of Action | Potential for Diarrhea |
|---|---|---|---|---|
| Osmotic | Draws water into the colon to soften stool. | MiraLAX (polyethylene glycol), Milk of Magnesia [1.4.2] | 1-3 days (MiraLAX); 30 min-6 hrs (Milk of Magnesia) [1.4.2] | Common [1.2.1] |
| Stimulant | Stimulates the intestinal muscles to contract and move stool along. | Dulcolax (bisacodyl), Senokot (senna) [1.4.2] | 6-12 hours [1.4.2] | More common and can be severe [1.2.1] |
| Bulk-Forming | Absorbs water to form a soft, bulky stool, stimulating a natural contraction. | Metamucil (psyllium), Citrucel (methylcellulose) [1.4.2] | 12-72 hours [1.4.2] | Common [1.2.1] |
| Stool Softener | Adds moisture directly to the stool to soften it. | Colace (docusate) [1.4.2] | 1-3 days [1.4.2] | Rare [1.2.1] |
Stimulant laxatives like Dulcolax are more likely to cause side effects such as cramping and diarrhea compared to MiraLAX [1.2.1]. Stool softeners like Colace rarely cause diarrhea [1.2.1].
Managing Diarrhea Caused by MiraLAX
If you experience diarrhea after taking MiraLAX, the first step is to stop taking it [1.2.2]. To manage the symptoms, focus on the following:
- Stay Hydrated: Diarrhea can lead to dehydration [1.2.1]. Drink plenty of fluids, such as water, broth, or electrolyte solutions, to replenish lost fluids [1.2.2, 1.8.1].
- Eat Bland Foods: Stick to a diet of bland foods like crackers, bananas, and broth until the diarrhea subsides [1.2.2].
If the diarrhea is severe, doesn't stop, or is accompanied by other concerning symptoms, you should contact your doctor [1.5.3].
When to Consult a Doctor
While MiraLAX is generally safe for short-term use, you should consult a healthcare professional in several situations:
- Your constipation lasts for more than 7 days of treatment [1.5.3].
- You experience severe or bloody diarrhea, rectal bleeding, or worsening stomach pain [1.2.4].
- You have signs of dehydration, such as dizziness, confusion, or infrequent urination [1.2.1, 1.12.1].
- You experience symptoms of a serious allergic reaction, such as hives, swelling of the face or throat, or difficulty breathing [1.2.1, 1.5.3].
Long-term use of MiraLAX without a doctor's supervision can lead to an electrolyte imbalance or dependency [1.5.3, 1.10.2].
Conclusion
So, can MiraLAX cause diarrhea? The answer is a clear yes. It's a common side effect resulting from its osmotic action of pulling water into the colon. While this helps relieve constipation, it can sometimes be too effective. The risk is heightened by taking more than the recommended dose and in older adults [1.2.2]. By following the proper dosage instructions, staying hydrated, and recognizing when to stop the medication, most users can manage this side effect effectively. For persistent or severe symptoms, it is always best to seek medical advice to ensure both safety and effective constipation relief.
For more information from an authoritative source, you can visit MedlinePlus.
