Is it okay to take MiraLAX and Benefiber in the same day?

January 10, 2026 •

4 min read

According to research published by the National Institutes of Health, over 14% of the U.S. population experiences chronic constipation, leading many to seek relief from over-the-counter options like MiraLAX and Benefiber. While both aim to improve bowel regularity, their distinct mechanisms of action raise questions about the safety of taking them concurrently. Understanding how these products work is crucial for effective and safe use.

Quick Summary

Taking MiraLAX and Benefiber on the same day is generally considered safe for occasional constipation, as they use different mechanisms to relieve symptoms. MiraLAX is an osmotic laxative that draws water into the colon to soften stool, while Benefiber is a bulk-forming fiber supplement that adds bulk to stool. Timing and hydration are key to managing their combined effects and minimizing side effects like bloating and gas.

Key Points

Generally Safe Combination: Taking MiraLAX and Benefiber on the same day is typically safe for occasional constipation, as they use different mechanisms.
Complementary Actions: MiraLAX, an osmotic laxative, softens stool with water, while Benefiber, a bulk-forming fiber, adds mass.
Risk of Side Effects: Combining them may increase gas, bloating, or cramping, which can be managed by adjusting doses and ensuring proper hydration.
Hydration is Key: Drinking plenty of fluids is essential for both products to work effectively and to prevent potential intestinal blockage from the added fiber bulk.
Professional Guidance: Individuals with chronic constipation, existing medical conditions, or those on other medications should consult a doctor before combining treatments.
Proper Timing: Separating the doses throughout the day can help mitigate potential gastrointestinal discomfort.
Monitor Effects: Pay attention to your body's reaction and stop use if you experience severe symptoms like pain or rectal bleeding.

Understanding the Mechanisms of MiraLAX and Benefiber

To understand whether these two products can be taken together, it's essential to first grasp their individual functions. While both are used to combat constipation, they belong to different classes of treatments and work in distinct ways within the digestive system.

How MiraLAX Works: The Osmotic Approach

MiraLAX, with the active ingredient polyethylene glycol 3350 (PEG 3350), is an osmotic laxative. Instead of adding fiber, it works by drawing water from the rest of the body into the colon. This influx of water hydrates and softens the stool, making it easier to pass. It is often recommended by doctors for the short-term treatment of occasional constipation and, in some cases, for chronic constipation. The effect is typically gentle and predictable, leading to a bowel movement within one to three days.

How Benefiber Works: The Fiber-Bulk Method

Benefiber is a bulk-forming fiber supplement containing wheat dextrin. It works by absorbing water in the digestive tract to create a bulkier, softer stool. This added bulk helps stimulate the natural muscle contractions (peristalsis) in the intestines, pushing the stool along more effectively. Benefiber acts as a prebiotic, nourishing the beneficial bacteria in the gut, which supports long-term digestive health. Unlike osmotic laxatives, it focuses on building stool mass rather than just hydrating it.

Combining MiraLAX and Benefiber: Safety and Strategy

Healthcare providers and clinical guidelines indicate that taking MiraLAX and Benefiber on the same day is generally acceptable and can be an effective strategy for managing constipation, particularly for complex cases or following certain medical procedures. Because their mechanisms are complementary rather than overlapping, they do not create a problematic drug interaction in the traditional sense.

However, proper timing and sufficient fluid intake are crucial to prevent uncomfortable side effects. For instance, some medical recommendations suggest taking a bulk-forming fiber like Benefiber with your largest meal and adding MiraLAX if constipation persists. You should always start with the minimum effective dose and increase gradually to avoid adverse effects.

Practical Tips for Taking Both

Hydration is non-negotiable: Both products rely on water to work properly. Without enough fluid, the added bulk from Benefiber can cause a blockage, and MiraLAX will not be able to soften the stool effectively.
Consider Timing: To minimize potential side effects like bloating and gas, you can separate the doses throughout the day. For example, take Benefiber with your morning meal and MiraLAX in the evening.
Listen to Your Body: Pay close attention to how your body responds. If you experience excessive bloating, gas, or diarrhea, you may need to adjust the dosage or discontinue one of the products.
Consult a Healthcare Provider: Before combining treatments, especially for chronic constipation, it is always best to speak with a doctor or pharmacist. They can provide personalized guidance based on your specific health needs and any other medications you might be taking.

Comparison of MiraLAX and Benefiber


Feature	MiraLAX	Benefiber
Active Ingredient	Polyethylene glycol 3350 (PEG 3350)	Wheat dextrin
Mechanism	Osmotic laxative; draws water into the colon to soften stool.	Bulk-forming fiber; absorbs water to create bulkier, softer stool.
Onset of Action	Gentle relief, typically within 1–3 days.	Gradual, with daily use promoting regularity over time.
Primary Use	Short-term relief for occasional or chronic constipation.	Daily fiber supplementation for digestive health and regularity.
Side Effects	Mild bloating, gas, nausea, or cramping.	Gas, bloating, and abdominal cramping, especially when starting.
Medication Interactions	No significant interactions expected; can be used with many other drugs.	Can affect the absorption of other medications, so separate doses by at least 2 hours.

Potential Side Effects and When to Be Cautious

While combining these products is generally safe, it can increase the likelihood of gastrointestinal side effects. The most common issues include increased gas, bloating, and abdominal cramping, as the body adjusts to the combined effects of bulk-forming fiber and osmotic action.

In rare cases, more serious symptoms may occur. You should stop taking the products and contact a doctor if you experience severe abdominal pain, persistent nausea, or rectal bleeding. This is especially important for individuals with pre-existing digestive conditions like inflammatory bowel disease or those who suspect a bowel obstruction, as the use of laxatives can be dangerous.

Who Should Exercise Caution?

Individuals with existing gastrointestinal issues: Those with conditions such as inflammatory bowel disease, irritable bowel syndrome (IBS), or a history of intestinal obstruction should consult a healthcare provider before use.
Those on other medications: Benefiber can affect the absorption of other drugs, so timing is important. A pharmacist can provide guidance on spacing medications appropriately.
Pregnant or breastfeeding women: Always consult a doctor before starting any new supplement or medication during pregnancy or breastfeeding.
Children: Use in children should always be under the guidance of a healthcare professional.

Conclusion

Taking MiraLAX and Benefiber on the same day is an option for managing constipation for many people, provided it's done with caution and proper timing. The two products work differently and complement each other's effects: MiraLAX softens stool through hydration, while Benefiber adds bulk through fiber. The most critical elements for safe and effective use are ensuring adequate hydration and listening to your body's response. While combining them is generally safe for short-term use, consulting a healthcare professional is the best course of action, especially for chronic issues or if you are taking other medications. This ensures a tailored approach that addresses your specific needs while minimizing the risk of side effects.

Mayo Clinic: Fiber supplements: Safe to take every day?

Frequently Asked Questions

A person might take MiraLAX and Benefiber together to combine the stool-softening effects of an osmotic laxative with the bulk-adding benefits of a fiber supplement, addressing different aspects of constipation simultaneously for more comprehensive relief.

No, it is often recommended to separate the doses to minimize the risk of excessive gas, bloating, and other GI discomfort. Taking them at different times of the day, such as one in the morning and one in the evening, is a common strategy.

Mixing them in the same drink is not ideal because the fiber in Benefiber can interact with MiraLAX, potentially affecting its efficacy or causing more side effects. It is better to take them in separate beverages.

The most common side effects of combining these two products are bloating, gas, and abdominal cramping due to the increased fiber and water in the colon. These symptoms often subside as your body adjusts.

Yes, adequate hydration is crucial when taking any fiber supplement or osmotic laxative. Drinking plenty of water helps both products work effectively and prevents the fiber from causing an obstruction.

An osmotic laxative like MiraLAX draws water into the colon to soften stool, while a bulk-forming fiber supplement like Benefiber adds mass to the stool, promoting natural bowel movements.

While MiraLAX is generally considered less likely to cause dependency than stimulant laxatives, long-term or excessive use of any laxative can alter the colon's function. Using a fiber supplement like Benefiber as a long-term dietary aid is less associated with dependency.