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Metamucil vs. MiraLAX: How do they compare?

Medically reviewed by Carmen Pope, BPharm. Last updated on Aug 7, 2025.

Official Answer by Drugs.com

Metamucil and MiraLAX are both brand names for over-the-counter constipation relief laxatives. This means they help you move bowel movements (feces) through your digestive system more easily.

Both laxatives come in a powder form that dissolves in water for drinking. However, they work through different mechanisms and have different recommended usage periods for treating constipation.

Metamucil for Constipation Relief

Metamucil is a bulk-forming laxative containing natural plant fiber called psyllium husk. Bulk-forming laxatives are not absorbed in your colon. They absorb water and help produce soft, bulky stools within 12 to 72 hours for constipation relief.

Because this fiber laxative works best for preventing constipation, you can take Metamucil daily as a dietary fiber supplement. You may start with one dose per day and gradually increase to 3 times daily if needed. The adult dosage for people ages 12 and over is one rounded teaspoon dissolved in 8 ounces of water. As a soluble fiber supplement, it adds grams of dietary fiber to your nutrition.

Not drinking enough water with Metamucil can cause choking or worsened constipation. Consult your healthcare provider before taking this bulk laxative if you have swallowing difficulties.

MiraLAX for Constipation Treatment

MiraLAX is an osmotic laxative containing polyethylene glycol 3350 (PEG 3350). This active ingredient draws fluid into your colon, where stool formation occurs. The additional fluid softens hard stools to provide constipation relief. You should expect watery bowel movements within 1 to 3 days.

The recommended MiraLAX dosage for people over age 17 is 17 grams, measured using the container cap. Mix the capful with 4 to 8 ounces of water until dissolved and drink. Do not exceed one daily dose or use MiraLAX for more than 7 days for occasional constipation.

Talk to your doctor before using MiraLAX if you have kidney disease or irritable bowel syndrome (IBS).

Important Safety Warnings

Always let your healthcare provider know if you have:

Contact your doctor know if you do not have a bowel movement within 7 days after taking laxatives. Always check with your pediatrician before giving any laxative to a child.

Natural Constipation Prevention Tips

To help prevent constipation naturally, eat plenty of dietary fiber from whole grains, fruits and vegetables, and drink adequate fluids throughout the day. Regular physical activity also helps maintain healthy bowel movements and prevents constipation.

References

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