What are the ingredients in macrogol laxatives? A Complete Breakdown

October 9, 2025 •

3 min read

Macrogol is considered one of the safest and most effective laxatives for treating both chronic constipation and faecal impaction. To understand how it works and what distinguishes different products, it is essential to know what are the ingredients in macrogol laxatives and how they function together.

Quick Summary

Macrogol laxatives primarily consist of the active ingredient macrogol (polyethylene glycol), which draws water into the stool. Many formulations also include electrolytes, flavorings, and sweeteners to improve taste and maintain the body's mineral balance.

Key Points

Active Ingredient: The primary active ingredient in macrogol laxatives is macrogol, also known as polyethylene glycol (PEG), which acts as an osmotic agent to increase water in the stool.
Electrolytes: Many formulations, especially those for chronic constipation or bowel cleansing, include electrolytes like sodium chloride, potassium chloride, and sodium bicarbonate to prevent dehydration and electrolyte imbalance.
Flavorings and Sweeteners: To improve palatability, most products contain inactive ingredients such as artificial sweeteners (acesulfame potassium, saccharin sodium) and various fruit flavorings.
Macrogol 3350 vs. 4000: Macrogol 3350 is often combined with electrolytes, whereas some Macrogol 4000 formulations are sold without them, which can affect the taste profile.
Key Difference in Products: The main difference between various macrogol laxative products often lies in whether they contain added electrolytes, which is crucial to consider for high-dose treatments.
Safety Considerations: Some products may contain sorbitol, which can be an issue for individuals with fructose intolerance, so it's important to check the full ingredient list.

The Core Ingredient: Macrogol (Polyethylene Glycol)

At the heart of every macrogol laxative is the active substance, macrogol, also known as polyethylene glycol (PEG). This is a long, linear polymer that is inert, non-absorbable, and not metabolised by the body. The number following the name, such as macrogol 3350 or macrogol 4000, indicates its average molecular weight.

Macrogol is an osmotic laxative, which means it works by retaining water in the intestinal lumen. By doing so, it increases the water content and volume of the stool, making it softer and easier to pass. This mechanism is gentle and works gradually, typically producing a bowel movement within 24 to 48 hours.

Formulations of Macrogol

Macrogol laxatives are primarily available as a powder designed to be dissolved in water before consumption. The different versions on the market, such as those available over-the-counter or on prescription, can be distinguished by their additional ingredients. One key difference is the presence or absence of electrolytes.

The Role of Electrolytes and Additional Salts

Many macrogol formulations are combined with electrolytes to ensure the body's salt balance is maintained. This is especially important for high-dose regimens used for conditions like faecal impaction or for bowel cleansing procedures before a colonoscopy. In these cases, a significant amount of fluid and salts is expelled from the body, and the added electrolytes help prevent dehydration and maintain normal electrolyte levels.

Common Electrolytes and Salts

Sodium chloride: Provides sodium and chloride ions, which are crucial for maintaining fluid balance and nerve function.
Potassium chloride: Supplies potassium, an essential mineral for proper cell function, particularly nerve and muscle cells.
Sodium bicarbonate: Helps regulate the body's pH balance.
Sodium sulfate: Often included in bowel cleansing preparations to increase the osmotic effect.
Ascorbic acid and sodium ascorbate: Present in some bowel prep products, contributing to the overall osmotic effect.

Other Ingredients: Flavorings and Sweeteners

To make the oral solution more palatable, manufacturers add flavorings and sweeteners. These excipients are inactive ingredients that improve the patient's experience without affecting the laxative's primary function.

Common Flavorings and Sweeteners

Acesulfame potassium (Acesulfame K): A calorie-free sweetener used to mask the taste of the macrogol and salts.
Saccharin sodium: Another artificial sweetener found in some formulations.
Flavoring agents: A variety of natural and artificial flavors are used, including orange, lemon, and lime oil.
Sorbitol: A sugar alcohol used as a sweetener. It is important to note for individuals with fructose intolerance, as sorbitol is converted to fructose in the body.

Macrogol Laxative Formulations: A Comparison

Understanding the subtle differences between products is key to choosing the right option. The main distinction is the inclusion of electrolytes.


Feature	Macrogol with Electrolytes (e.g., Movicol, Laxido)	Macrogol without Electrolytes (e.g., Forlax, generic PEG 4000)
Primary Function	Treat chronic constipation and faecal impaction.	Treat chronic constipation.
Active Ingredient	Macrogol 3350.	Macrogol 4000.
Electrolyte Content	Contains sodium chloride, potassium chloride, and sodium bicarbonate.	No added electrolytes.
Risk of Electrolyte Imbalance	Very low risk, as electrolyte levels are balanced.	Very low risk for standard use, as minimal absorption occurs.
Palatability	Often described with a saltier or more medicinal taste due to the electrolytes.	Generally considered to have a more pleasant or neutral taste.
Special Considerations	Recommended for high-dose use (bowel prep) to prevent salt loss.	May be preferable for patients on a low-sodium diet, but still contains trace amounts.

Ingredients to Check for Specific Needs

For individuals with certain dietary restrictions or intolerances, examining the full list of ingredients is essential. For instance, some products containing specific flavorings may not be suitable for those with sensitivities. As mentioned, some formulations include sorbitol, which can cause issues for those with fructose intolerance. Always review the product leaflet or consult a pharmacist to ensure the product is safe for your specific health needs.

Conclusion: More Than Just the Active Ingredient

Macrogol laxatives are a highly effective treatment for constipation due to their primary active ingredient, macrogol (PEG). However, a full understanding of their ingredients requires looking beyond just the laxative agent. The addition of electrolytes in many formulations is a critical safety feature, particularly for intensive use, while the inclusion of flavors and sweeteners significantly improves the patient experience. As with any medication, reading the full list of ingredients is the best way to ensure a product is appropriate for your specific health circumstances.

For more detailed information on macrogol, consult authoritative medical resources such as the National Institutes of Health.(https://pmc.ncbi.nlm.nih.gov/articles/PMC6267542/)

Frequently Asked Questions

The active ingredient is macrogol, which is a type of polyethylene glycol (PEG). It is an osmotic agent that works by drawing water into the bowel to soften stools.

No, not all macrogol laxatives contain electrolytes. Some formulations, particularly those with macrogol 4000, are available without added electrolytes. Many others, especially those based on macrogol 3350, do contain them.

Electrolytes like sodium chloride and potassium chloride are added to prevent dehydration and mineral imbalances, especially when taking high doses of the laxative for conditions like faecal impaction or bowel preparation.

Common sweeteners include acesulfame potassium and saccharin sodium. Flavorings often include ingredients like lemon, lime, or orange oil to improve the taste.

Clinical trials have shown no significant difference in the effectiveness of macrogol with or without electrolytes for treating constipation in adults. The choice often comes down to taste preference and specific health needs, such as avoiding high sodium intake.

Patients with fructose intolerance should be cautious. Some macrogol products contain sorbitol, a sugar that is converted to fructose in the body and should be avoided by those with this condition.

Macrogol is minimally absorbed into the bloodstream and is not broken down in the body. It passes through the gastrointestinal tract and is excreted almost entirely unchanged.

The number refers to the average molecular weight. Macrogol 3350 and 4000 are both high-molecular-weight polymers that work similarly. The main difference in products is usually the additives; Macrogol 3350 products often include electrolytes, while some Macrogol 4000 versions do not.