At a glance
Miralax (polyethylene glycol 3350, known in the UK as macrogol or by brand names like Movicol and Laxido) is one of the most commonly discussed stool management options for people with anal fissures. It is an osmotic laxative — it works by drawing water into the stool, making it softer and easier to pass.
This guide covers how it works, what people report about using it for fissure management, and practical tips for getting the most from it.
How it works
Miralax is a powder that dissolves in water or other liquids. Once consumed, it passes through the digestive tract without being absorbed. In the colon, it draws water into the stool through osmosis, increasing the water content and making the stool softer and bulkier.
Key points:
- It is not a stimulant laxative — it does not force the bowel to contract
- It is not habit-forming — the bowel does not become dependent on it
- It works gradually — effects are typically seen within one to three days
- It requires adequate hydration to work properly — if you are dehydrated, it has less water to draw from
Why stool management matters for fissures
A fissure is a tear in the lining of the anal canal. Every bowel movement passes over that tear. If the stool is hard or requires straining, the tear is re-traumatised and healing is set back. Soft stools that pass easily give the fissure the best chance to heal.
This is why stool management is the foundation of fissure care — not an optional extra.
What people report
Positive experiences
- Softer stools within a day or two of starting regular use
- Less pain during bowel movements as a direct result of softer stools
- Easy to take — dissolves in water with no taste or gritty texture
- Consistent results when used daily with adequate water
- Combines well with other stool management — fibre, docusate, hydration
Common issues
- Finding the right dose — too little and stools remain firm; too much and they become loose or watery
- Diarrhoea at higher doses — which can irritate a fissure just as much as hard stools
- Needing to drink more water — Miralax needs water to work, so hydration becomes more important
- Gas and bloating in some people, particularly in the first few days
Practical tips
Starting
- Begin with the standard dose on the packaging
- Take it at the same time each day — consistency helps
- Dissolve completely in a full glass of water or clear liquid
- Give it two to three days before adjusting the dose
Adjusting
- If stools are still too firm after three days, increase slightly
- If stools become loose or watery, reduce the dose
- The goal is a type 4 on the Bristol stool scale — smooth, soft, sausage-shaped
- Small adjustments make a bigger difference than you might expect
Hydration
- Drink at least an additional glass of water on top of your normal intake when using Miralax
- The product draws water from your body into the stool — you need to replace it
- If you are not drinking enough, the product will be less effective
How long to continue
- Most people use Miralax daily throughout the active healing period of their fissure
- As the fissure improves, some people transition to fibre supplements alone
- Stopping abruptly can lead to a return of harder stools, so tapering is generally better than stopping suddenly
- Discuss duration with your clinician
Miralax vs other options
People often ask how Miralax compares to other stool management products:
- Miralax vs docusate sodium — different mechanisms. Miralax draws water in; docusate acts as a surfactant to soften stool. Many people use both together.
- Miralax vs lactulose — both are osmotic agents. Lactulose can cause more gas and bloating in some people. Miralax is generally described as having fewer side effects.
- Miralax vs fibre supplements — fibre adds bulk and promotes regularity; Miralax adds water content. They work well together.
- Miralax vs stimulant laxatives — Miralax is gentler and better suited for ongoing use. Stimulant laxatives can cause cramping and urgency that is uncomfortable with a fissure.