Low-volume options, compared
In short
"Low-volume" prep is a marketing phrase as much as a clinical one. It generally means the medicated drinking volume is around a litre per dose rather than two — but the additional clear-fluid intake required is large in every case, and a smaller volume of medicine does not mean a shorter prep or less time near a bathroom. Low-volume options sit in three chemical families: low-volume PEG with ascorbate (MoviPrep, Plenvu), sulfate-based (SUPREP, Sutab), and sodium picosulfate with magnesium citrate (CLENPIQ, Picolax, Citrafleet). Each has different trade-offs.
What this page covers
What "low-volume" actually means, the products available across North America, the UK, and Europe, how they compare on volume, taste, electrolyte profile, and safety, and how to think about which trade-off matters most for you.
- The honest definition of low-volume
- The three chemical families
- A side-by-side comparison table
- Who is typically offered which
- Choosing well, given your priorities
What "low-volume" really means
The original four-litre PEG preps were effective and well tolerated by people who could finish them. The most important reason a prep fails is not the chemistry but the unfinished bottle on the kitchen counter. Manufacturers responded by formulating products that do the same job in less drinking volume — by adding ascorbate, by switching to a sulfate-based osmotic, or by combining a stimulant laxative with an osmotic salt.
The medicated drinking volume is genuinely smaller in these products: typically around half a litre to one litre per dose, rather than two. The total fluid intake is not. Most low-volume products specify around a litre of additional clear fluid per dose, taken in a defined window. Skipping this clear fluid is the main cause of dehydration, headache, and inadequate cleansing in low-volume preps.
The honest summary, in other words: "low-volume" describes the cup you do not want to drink, not the total liquid you must finish. The bathroom timetable is essentially the same.
The three chemical families
Low-volume PEG with ascorbate. PEG combined with ascorbic acid (vitamin C) and ascorbate salts. The ascorbate increases the osmotic pull, allowing a smaller dose of PEG to do the same work. MoviPrep and Plenvu are the leading examples. Generally well tolerated. Avoid in glucose-6-phosphate dehydrogenase (G6PD) deficiency and certain other inherited conditions.
Sulfate-based. A combination of sodium, potassium, and magnesium sulfates that pull water into the bowel by osmosis. SUPREP (liquid) and Sutab (tablet) are the main products in North America; Eziclen and Izinova are similar formulations available outside the United States. Caution in advanced kidney disease, heart failure, and liver disease.
Sodium picosulfate with magnesium citrate. A stimulant laxative (sodium picosulfate) combined with an osmotic salt (magnesium citrate). The smallest medicated drinking volume on the market — typically around a third of a litre per dose, premixed in CLENPIQ or made up from sachets in Picolax and Citrafleet. Effectiveness depends heavily on adequate clear-fluid intake. Caution in kidney disease.
Side by side
This table brings the most common low-volume options together. Volumes are approximate and depend on product version and country. The "additional clear fluid per dose" column is the part most people underestimate.
| Product | Family | Medicated volume per dose | Additional clear fluid per dose | Taste | Electrolyte / safety profile |
|---|---|---|---|---|---|
| MoviPrep | Low-volume PEG with ascorbate | About one litre | About half a litre | Citrus / lemon; some find the ascorbate aftertaste sour | Generally well tolerated. Avoid in G6PD deficiency. |
| Plenvu | Low-volume PEG with ascorbate and sulfate | About half a litre | About half a litre | Mango or fruit-punch flavoured; quite sweet | Smallest PEG volume. Avoid in G6PD deficiency and certain inherited disorders. |
| SUPREP | Sulfate-based liquid | About half a litre (diluted) | About one litre | Strongly salty under fruit flavouring | Fluid-shifting. Caution in advanced kidney, heart, liver disease. |
| Sutab | Sulfate-based tablets | Tablets plus measured cups (about half a litre per dose) | About one litre | No salty taste at the lips; some develop nausea later | Same fluid-shifting profile as SUPREP. Avoid in significant swallowing disorders. |
| CLENPIQ | Sodium picosulfate / magnesium citrate (premixed) | About a third of a litre | About one litre, with additional fluid through the evening | Cranberry; many find this the most palatable option | Stimulant plus osmotic. Caution in kidney disease. Magnesium and potassium shifts possible. |
| Picolax / Citrafleet | Sodium picosulfate / magnesium citrate (sachets) | About a quarter of a litre per sachet (made up) | Substantial additional clear fluid required, often more than a litre per dose | Orange / lemon; pleasant by prep standards | Same family as CLENPIQ; same cautions. |
Who is typically offered which
Patterns vary by country and clinic, but the rough logic is consistent.
People with kidney disease beyond a certain stage, with heart failure, or with significant liver disease are usually steered toward iso-osmotic PEG — high- or low-volume — rather than sulfate or picosulfate-based products, because these families shift fluid and electrolytes more aggressively. The small medicated volume of CLENPIQ does not change this.
People who have not tolerated salty preps in the past are often offered MoviPrep, Plenvu, or one of the picosulfate / magnesium citrate products. People who struggle with large drinking volumes more than with taste are often offered Plenvu or CLENPIQ. People who cannot swallow tablets easily are routinely steered away from Sutab.
People with G6PD deficiency, phenylketonuria, or certain other inherited conditions are generally not given ascorbate-containing low-volume PEG, and are offered an alternative.
For older adults, frail patients, and patients on multiple medications that affect kidneys or electrolytes, the cautious choice is often a PEG product (high- or low-volume) rather than sulfate or picosulfate, with extra attention to clear-fluid intake. None of these patterns is absolute, and the prescribing clinician's view of your specific case overrides every general rule.
Choosing well, given your priorities
If your prep is failing because of one specific problem, naming that problem helps your clinician choose. The most common failure modes are:
Volume. If you cannot drink large amounts of liquid in a short window, the smallest-volume options are CLENPIQ, Picolax, and Citrafleet (sodium picosulfate / magnesium citrate), followed by Plenvu and SUPREP (about half a litre of medicated fluid per dose). Plan the additional clear-fluid intake carefully; this is where these products fail.
Taste. If salty drinks make you gag, the picosulfate / magnesium citrate products are the most palatable, followed by MoviPrep (lemony) and Plenvu (sweet). SUPREP and the high-volume PEG products tend to be the least palatable. Sutab avoids the taste issue entirely if you can swallow tablets.
Swallowing. If swallowing is the problem rather than taste, Sutab is not the answer despite its convenience marketing. A liquid prep is usually better.
Kidney function or fluid balance. If your kidneys, heart, or liver are the limiting factor, iso-osmotic PEG (high- or low-volume) is generally preferred, regardless of how the marketing reads. The smallest-volume products are not the safest products.
Previous failed prep. If a low-volume prep has failed to clean you out before, the next attempt is usually high-volume PEG with extended dietary preparation, not a different low-volume product. The cleansing job is the constraint, not the cup.
What to ask your clinician
- Why have you chosen this particular low-volume prep for me, given my history?
- What is the total fluid intake you are asking me to drink across the prep — medicated and clear?
- If I had a problem with a previous prep — taste, vomiting, dehydration, incomplete cleansing — which prep would you choose differently this time?
- Are there any of my medications, including supplements, that I should pause or adjust around this prep, and who is making that decision?
- Does my kidney function, recent enough to be reliable, support this choice?
- What signs would tell me this prep is not working, and at what point should I call the unit?
Common worries, briefly addressed
Are low-volume preps less effective?
Used correctly, with the full additional clear fluid taken on schedule, the major low-volume preps produce cleansing comparable to high-volume PEG in clinical trials. The "used correctly" qualifier matters. The most common reason a low-volume prep produces a poor result is that the additional clear fluid was reduced.
Is the smallest one always the easiest?
No. CLENPIQ has the smallest medicated drinking volume but requires substantial clear-fluid intake afterward, and produces a similar bathroom timetable. The "easy" prep is the one whose specific trade-off — taste, volume, salt load, tablets — fits your own difficulty.
Is one of these safer than the others?
For a healthy adult, all of these products are widely used and safe when taken as prescribed. For people with kidney, heart, or liver disease, iso-osmotic PEG products are generally the safer choice. The decision is a clinical one and belongs with your prescribing clinician.
Can I switch products partway through?
Not on your own. If a prep is not working — vomiting, severe distress, no output after a couple of hours — call the unit. They may give a specific instruction, including switching products, but this is not a substitution to make at home.
Sources
- American College of Gastroenterology — clinical guideline on bowel preparation
- American Society for Gastrointestinal Endoscopy — bowel preparation product information
- U.S. Multi-Society Task Force on Colorectal Cancer — bowel preparation consensus
- European Society of Gastrointestinal Endoscopy — guideline on bowel preparation for coloscopy
- National Institute for Health and Care Excellence — guidance referenced by NHS bowel cancer screening
- British Society of Gastroenterology — quality standards for bowel preparation
- Canadian Association of Gastroenterology — bowel preparation position statements