Key takeaways:
Linzess (linaclotide) is a prescription medication that treats chronic (long-term) constipation, while Miralax (polyethylene glycol) is an over-the-counter laxative for occasional constipation.
Miralax generally leads to a bowel movement in 1 to 3 days. It’s usually a short-term treatment that you take as needed. Linzess typically starts working within 1 week, but you need to take it every day for ongoing symptom relief.
Both medications can cause nausea, gas, and diarrhea. Linzess may also raise the risk of heartburn or more frequent upper respiratory infections. Contact your healthcare team if you experience severe or persistent diarrhea while taking either medication.
Linzess and Miralax are both available as brand-name medications. But you can also find Miralax as a lower-cost generic. GoodRx can help make your prescription more affordable.
Save on related medications
If you’ve been dealing with constipation, you’re not alone — and there are lots of treatments that can help. Two common options are Linzess (linaclotide) and Miralax (polyethylene glycol) but they work in different ways and are used for different types of constipation.
Your prescriber or pharmacist might suggest Linzess or Miralax based on your symptoms and health needs. In this article, we’ll break down seven key differences between Linzess versus Miralax, including how they work, what they treat, and what side effects to watch for.
Linzess vs. Miralax comparison chart
The main differences between Linzess versus Miralax are detailed in the chart below.
Linzess | Miralax | |
Prescription required? | Yes | No |
Approved for chronic constipation? | Yes | No |
Approved for IBS-C? | Yes | No |
Approved for occasional constipation? | No | Yes |
Onset of action | 1-2 weeks | 1-3 days |
Safe to take long-term? | Yes | Not without a healthcare professional’s OK |
Let’s take a closer look at these differences to help you find the right treatment for your needs.
1. Linzess and Miralax are approved for different health conditions
Linzess is FDA approved to treat chronic (long-term) constipation for people living with the following conditions:
Irritable bowel syndrome with constipation (IBS-C) for adults
Chronic idiopathic (unknown cause) constipation (CIC) for adults
Functional constipation (FC) for children ages 6 to 17
Miralax is only approved to relieve occasional constipation. It isn’t approved for chronic constipation, and children under age 17 shouldn’t take it without a healthcare professional’s OK.
2. Linzess is only available by prescription, while Miralax is sold OTC
Linzess is only available with a prescription from a licensed healthcare professional. If you’re interested in trying it, you’ll need to schedule an appointment with your healthcare team. They can help decide if it’s right for you. Note that Linzess is currently only available as a brand-name medication.
Miralax and its generic versions are conveniently available over-the-counter (OTC). You don't need a prescription from a healthcare professional to purchase it. Polyethylene glycol, the active ingredient in Miralax, is also available by prescription. This may offer additional savings if your prescription insurance covers it.
When is constipation an emergency? Learn how to tell when it’s time to see a healthcare professional for constipation.
Best (and worst) drinks for constipation: These beverages can help get things moving if you’re constipated.
Understanding IBS: This guide explains the symptoms, diagnosis, and treatment for IBS.
3. Linzess and Miralax work differently to treat constipation
Linzess is a type of medication called a guanylate cyclase-C agonist. It works by activating a protein that tells your intestines to release more fluid into your stool. This helps soften stool and move it through your digestive tract. Linzess also helps ease constipation-related pain by blocking certain nerve signals in your gut.
Miralax is an osmotic laxative. As the name suggests, it works by a process called osmosis. Osmosis is the movement of water. Miralax helps pull more water into your intestines as the medication passes through your gut. The added water softens your stool and helps it move through the digestive tract, making it easier to pass.
Miralax doesn’t help with constipation-related pain. And it only pulls fluid into your intestines as it passes through your body. Linzess, on the other hand, changes how your gut works for long-term constipation relief.
4. Linzess and Miralax come in different doses and dosage forms
Miralax comes as a powder that you mix a liquid then drink. The usual dosage is 17 g of powder mixed in 4 oz to 8 oz of liquid once daily. You can take Miralax as needed for constipation, but you shouldn’t take it for more than 7 days in a row without a healthcare professional’s OK.
Linzess comes as an oral capsule in three doses: 72 mcg, 145 mcg, and 290 mcg. The typical Linzess dosages are 290 mcg once daily for IBS-C and 145 mcg once daily for CIC. Children typically take 72 mcg of Linzess once daily. You need to take Linzess on a daily basis in order for it to work properly.
Most people swallow Linzess capsules whole. But if you or your child have trouble swallowing pills, you can open the capsule and sprinkle the contents onto a spoonful of applesauce or a small amount of water. Your pharmacist or prescriber can give you instructions for this if needed.
5. Linzess takes longer to work than Miralax, but it provides better long-term relief
Neither Linzess nor Miralax work right away to treat constipation. Miralax usually leads to a bowel movement within 1 to 3 days. Some people feel relief within 24 hours after taking Linzess, but it may take up to 1 week to reach its full effect.
Miralax will likely produce a bowel movement faster than Linzess. But keep in mind that its effects aren’t long lasting, since it only works as it moves through your system. And it isn’t meant for everyday use.
Linzess takes a little longer to work, but it will continue to treat chronic constipation as long as you take it.
6. Linzess and Miralax have similar side effects, but there are some differences between them
Linzess and Miralax share some common side effects, such as:
Nausea
Gas
Bloating
Diarrhea
You can help reduce these side effects by eating smaller, more frequent meals and avoiding carbonated, fried, or spicy foods. Staying hydrated can also help manage side effects as well as improve constipation. For either medication, seek medical care if you develop severe or long-lasting diarrhea
Linzess may also cause other side effects, such as heartburn and more frequent upper respiratory infections. Your prescriber can suggest management options if these become an issue for you.
7. There are ways to save on the cost of Linzess and Miralax
GoodRx can help you find ways to save on the cost of both Linzess and Miralax.
Linzess
Linzess is only available as a brand-name medication. GoodRx can help you navigate between patient assistance programs and copay savings cards to save money on your prescription.
Save with a copay savings card. If you have commercial insurance, you may be eligible to pay as little as $30 for Linzess using a savings card from the manufacturer.
Save with patient assistance programs. AbbVie is the manufacturer of Linzess. If you’re uninsured or underinsured, you may be eligible for AbbVie’s patient assistance program, which offers the medication free of cost.
Miralax
Miralax is available as both a brand-name and generic medication. By having a healthcare professional write a prescription for OTC Miralax, GoodRx can help you save over 90% off the average retail price. Generic Miralax's price at certain pharmacies is less than $16.12 with a free GoodRx discount.
The bottom line
When it comes to Linzess (linaclotide) versus Miralax (polyethylene glycol), both medications treat constipation, but they differ in several key ways. Linzess is a prescription medication, while Miralax is available over the counter. Linzess is FDA approved for treating chronic (long-term) constipation in adults and children ages 6 and older. Miralax is approved only for occasional constipation, and children shouldn’t take it without a healthcare professional’s OK.
Linzess generally takes effect within 1 week, but it’s safe to take long-term for ongoing symptom relief. Miralax works faster — usually within 1 to 3 days — but you should only take it as needed, for no more than 7 days at a time unless your prescriber tells you otherwise.
Your healthcare team can help determine whether Linzess or Miralax is a better fit for your constipation symptoms.
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References
Allen, P., et al. (2024). Pediatric functional constipation. StatPearls.
Allergan. (2023). Linzess- linaclotide capsule, gelatin coated [package insert].
Atlantic Biologicals. (2018). Polyethylene glycol 3350- polyethylene glycol 3350 powder, for solution [package insert].
Bassotti, G., et al. (2021). Chronic idiopathic constipation in adults: A review on current guidelines and emerging treatment options. Clinical and Experimental Gastroenterology.
Cardinal Health 107. (2025). Miralax- polyethylene glycol 3350 powder, for solution [package insert]. DailyMed.
