Polyethylene Glycol 3350 With Electrolytes

What it is

Polyethylene glycol 3350 with electrolytes is a powder that is dissolved in water and drunk. The active bulk is PEG 3350, a synthetic polymer of average molecular weight about 3,350 g/mol that is barely absorbed from the gut and is not fermented by gut bacteria. The electrolyte salts are mixed in with it: a 4 litre GoLYTELY jug contains 236 g of PEG 3350 plus 22.74 g sodium sulfate, 6.74 g sodium bicarbonate, 5.86 g sodium chloride and 2.97 g potassium chloride. Products differ: bowel-cleansing solutions are made up to litres of fluid, while European constipation products are single sachets of about 13 g of macrogol 3350 with the same salts.

What the research says

The evidence for what it does is strong for one thing and weaker for others. For emptying the colon before a colonoscopy it is the reference treatment, though trials show even a full preparation produces an adequate clean in only around half of hospitalised patients. For ordinary constipation, pooled randomised evidence shows it adds roughly two bowel movements a week compared with placebo and beats lactulose, in adults and, with much weaker evidence, in children. It does not relieve abdominal pain in IBS-C. The electrolytes, which give the product its name, have not been shown to add any benefit over plain PEG 3350 for constipation. Harms are mostly gastrointestinal and mild, but the large lavage doses can disturb fluid and salts enough to cause seizures, arrhythmias and kidney injury, and PEG itself can cause anaphylaxis.

Evidence grade: Well established.

How it works

Drug class: Osmotic laxative (macrogol / polyethylene glycol) combined with sodium and potassium salts; used as a colonic lavage solution and as a laxative

Polyethylene glycol 3350 is a large, water-loving polymer that the gut barely absorbs and gut bacteria do not ferment. It holds water inside the bowel, which softens stool and increases stool volume so the bowel empties. The added electrolytes (sodium sulfate, sodium chloride, sodium bicarbonate, potassium chloride) are there to limit net movement of salts and water across the gut wall when large lavage volumes are drunk, which is why they were originally added for pre-procedure lavage rather than for everyday laxative use. (Source 1)

What it is used for

• This is the use PEG 3350 with electrolytes was developed for and the use it is approved for in the US. Randomised trials compare one PEG-electrolyte regimen with another rather than with placebo, so the trial literature is about which regimen cleans best and is best tolerated, not about whether lavage works. In hospitalised patients a 2 L PEG plus ascorbate regimen was non-inferior to the classic 4 L PEG-electrolyte solution, and adequate preparation was achieved in only about half of patients in either arm. Evidence: established. (Source 2)
• The evidence that macrogol/PEG raises stool frequency is good: a network meta-analysis of 19 trials and 2,247 patients found PEG with and without electrolytes each added about 1.8-1.9 bowel movements a week versus placebo and both beat lactulose. Note the regulatory split: in the US the PEG 3350 plus electrolytes products are labelled only for bowel cleansing, so daily use for constipation is off-label there, while macrogol 3350 with electrolytes is licensed for constipation in the UK and EU. The same analysis found the electrolytes add nothing to efficacy or tolerability. Evidence: established. (Source 3)
• A Cochrane review of 25 trials and 2,310 children found PEG beat placebo by 2.61 stools per week and lactulose by 0.70 stools per week, but graded the evidence low to very low certainty because of sparse data, heterogeneity and high risk of bias, and found no difference between PEG and dietary fibre, liquid paraffin or enemas. The US PEG-electrolyte label states that paediatric safety and effectiveness have not been established. Evidence: limited. (Source 4)
• One 139-patient randomised trial of PEG 3350 plus electrolytes in IBS-C improved bowel movements versus placebo but did not improve abdominal discomfort or pain compared with placebo. So it treats the constipation part of IBS-C and not the pain part, on the strength of a single short trial. Evidence: limited. (Source 5)

Interactions

• Any oral medicine taken around the same time (label): A bowel-cleansing volume of PEG with electrolytes flushes the gut and can reduce how much of other swallowed medicines is absorbed. The label tells prescribers to give oral medicines in the hour before the preparation starts. (Source 6)
• Stimulant laxatives (bisacodyl, sodium picosulfate) (label): Taking a stimulant laxative at the same time is reported to raise the risk of damage to the lining of the colon and of ischaemic colitis. (Source 7)
• Diuretics, ACE inhibitors, angiotensin receptor blockers and NSAIDs (label): These medicines affect kidney handling of salt and water, so combining them with a large lavage volume raises the risk of kidney injury and electrolyte disturbance; the label advises hydration and blood tests. (Source 8)
• Potassium supplements and potassium-affecting drugs, and sodium-restricted diets (clinical trial): The electrolyte version delivers sodium and potassium salts. One trial in the pooled review found measurable absorption of electrolytes even from low doses of PEG with electrolytes, which matters for anyone on a salt-restricted diet; a case of mild hypokalaemia occurred in a patient taking PEG with electrolytes together with a diuretic. (Source 9)
• Starch-based food and drink thickeners (case reports): PEG thins starch-thickened liquids. When a PEG product was mixed into pre-thickened drinks used by people with swallowing problems, the liquid thinned and choking and possible aspiration were reported, so the two should not be combined. (Source 10)
• Alcohol (label): No study of drinking alcohol together with PEG with electrolytes was found. The only alcohol-related statement in the label is indirect: people withdrawing from alcohol are listed among those at higher risk of seizure if the preparation disturbs their electrolytes. The preparation itself requires clear liquids only. (Source 8)
• Red and purple drinks and food colourings (label): Not a pharmacological interaction: red and purple liquids can stain the colon lining and be mistaken for blood at colonoscopy, so the label tells patients to avoid them during the preparation. (Source 11)

Stopping it

• PEG 3350 with electrolytes is not known to cause dependence or a withdrawal syndrome, and no deprescribing or tapering trial was found. The longest safety data in the pooled review come from a 12 month open-label study of PEG that found no clinically significant change in blood chemistry, including electrolytes, over a year, in the whole population or in older participants. (Source 12)
• Cochrane's reviewers say plainly that long-term use has not been studied properly in children, so there is no trial evidence to say what happens when a child who has been taking it for months stops. (Source 13)
• For bowel cleansing the question of stopping does not arise: it is a single course taken the evening before, or split around, the procedure, and the end point is a clear rectal effluent. (Source 2)

What goes wrong

Gastrointestinal adverse events were the common harm in the IBS-C trial, at low single-figure rates and barely above placebo for diarrhoea. (Source 5)

• Randomized trial, Moderate certainty.
• Size: 139 randomised.
• Who: adults with constipation-predominant IBS.
• How long: 28 days.
• Result: abdominal pain 4.5% with PEG 3350+E versus 0% with placebo; diarrhoea 4.5% versus 4.3%.
• Funding: not stated in the record we read.

The most common drug related treatment-emergent adverse events were abdominal pain (PEG 3350+E, 4.5%; placebo, 0%) and diarrhoea (PEG 3350+E, 4.5%; placebo, 4.3%).

More patients stopped PEG with electrolytes than plain PEG because of adverse events in the pooled trials. (Source 14)

• Meta-analysis, Low certainty.
• Size: 12 studies supplied safety data within the 19-study review.
• Who: adults with functional constipation.
• How long: short-term trials.
• Result: discontinuation for adverse events 11/612 equivalent (1.8%) on PEG+E versus 3 patients (0.4%) on PEG; reasons included abdominal pain, abdominal rigidity, bloating, nausea, diarrhoea, anal fissure and poor taste.
• Funding: medical writing and statistics funded by Key Pharmaceuticals Pty Ltd, which markets PEG without electrolytes.

Eleven patients (1.8 %) discontinued therapy due to adverse events with PEG + E compared to three patients (0.4 %) with PEG.

Laboratory changes were rare in the constipation trials; one case of mild hypokalaemia occurred on PEG with electrolytes taken with a diuretic. (Source 15)

• Meta-analysis, Low certainty.
• Size: 12 studies with safety data.
• Who: adults with functional constipation.
• How long: short-term trials.
• Result: one case of mild hypokalaemia on PEG+E with concurrent diuretic use; no other clinically relevant laboratory or vital-sign changes.
• Funding: medical writing and statistics funded by Key Pharmaceuticals Pty Ltd.

Overall, there were no clinically relevant changes in laboratory measures or vital signs, with the exception of one case of mild hypokalaemia in a patient taking PEG + E with concurrent diuretic use

In hospitalised patients given full bowel preparation, electrolyte disturbance and acute kidney injury occurred at low single-figure rates with no difference between a 2 L and a 4 L regimen. (Source 16)

• Randomized trial, Moderate certainty.
• Size: 520 randomised (2L PEG+ASC n=257; 4L PEG-ELS n=263)
• Who: hospitalised adults undergoing colonoscopy.
• How long: single preparation.
• Result: hyponatraemia 1.6% versus 3.3% (P=0.50); hypokalaemia 5.3% versus 8.7% (P=0.27); hyperkalaemia 1.1% versus 0.0% (P=0.24); acute kidney injury 4.3% versus 3.3% (P=0.73)
• Funding: not stated in the record we read (NCT05054036)

No significant difference was detected with regard to hyponatremia (1.6% vs. 3.3%, P =0.50), hypokalemia (5.3% vs. 8.7%, P =0.27), hyperkalemia (1.1% vs. 0.0% P =0.24), or acute kidney injury (4.3% vs. 3.3%, P =0.73).

A PEG-electrolyte lavage solution with ascorbic acid produced reproducible severe hyponatraemia with seizures in an older man with undiagnosed SIADH. (Source 17)

• Case report, Very low certainty.
• Size: 1 patient.
• Who: a 79-year-old man preparing for colonoscopy.
• How long: two separate preparation episodes.
• Result: stupor and generalised tonic-clonic seizures; serum sodium 119 mmol/L; symptoms recurred on re-exposure.
• Funding: not stated.

After completing bowel preparation, stupor and generalized tonic-clonic seizures developed. His serum sodium level was 119 mmol/L.

The US label records anaphylaxis, seizures, arrhythmias, ischaemic colitis, Mallory-Weiss tears and oesophageal perforation as reported harms, with nausea, fullness and bloating in up to half of patients. (Source 6)

• Official position, Certainty not rated.
• Size: postmarketing reports of uncertain denominator plus clinical trials.
• Who: adults given PEG 3350 with electrolytes for colon cleansing.
• How long: single preparation course.
• Result: nausea, abdominal fullness and bloating in up to 50% of patients; other events reported voluntarily with frequency that cannot be reliably estimated.
• Funding: label holder Azurity Pharmaceuticals; this is a regulatory position dated 1/2026, not a trial.

Nausea, abdominal fullness and bloating are the most common adverse reactions (occurred in up to 50% of patients).

What the evidence supports

Polyethylene glycol with and without electrolytes each increased weekly bowel movements compared with placebo and with lactulose in adults with functional constipation. (Source 3)

• Meta-analysis, Moderate certainty.
• Size: 2,247 patients across 19 studies in the network meta-analysis.
• Who: adults with functional constipation.
• How long: mostly short trials (defecation frequency assessed after about 2 weeks or at end of treatment)
• Result: PEG +1.8 bowel movements/week (95% Crl 1.0, 2.8) and PEG+E +1.9 (95% Crl 0.9, 3.0) versus placebo; +1.8 (95% Crl 0.0, 3.5) and +1.9 (95% Crl 0.2, 3.6) versus lactulose.
• Funding: the medical writer and the statistician were funded by Key Pharmaceuticals Pty Ltd, which markets PEG without electrolytes; the authors declared no competing interests.

PEG and PEG + E are both effective, increasing the number of bowel movements per week by 1.8 (95 % Crl 1.0, 2.8) and 1.9 (95 % Crl 0.9, 3.0) respectively versus placebo

In children, PEG increased stools per week compared with placebo and with lactulose, but Cochrane rated the certainty low to very low. (Source 4)

• Systematic review, Low certainty.
• Size: 25 randomised trials, 2,310 participants (2 trials, 101 patients, for the placebo comparison; 6 trials, 465 patients, for lactulose)
• Who: children aged 0-18 with functional constipation.
• How long: short follow-up.
• Result: PEG versus placebo MD 2.61 stools/week (95% CI 1.15 to 4.08); PEG versus lactulose MD 0.70 (95% CI 0.10 to 1.31); 18% (27/154) of PEG patients needed additional laxatives versus 31% (47/150) on lactulose (RR 0.55, 95% CI 0.36 to 0.83)
• Funding: not stated in the review record we read.

Meta-analysis of two studies (101 patients) comparing polyethylene glycol (PEG) with placebo showed a significantly increased number of stools per week with PEG (MD 2.61 stools per week, 95% CI 1.15 to 4.08).

A higher PEG dose produced more stools per week than a lower dose in children, showing a dose-response. (Source 4)

• Randomized trial, Low certainty.
• Size: 1 study, 90 participants.
• Who: children with functional constipation.
• How long: short.
• Result: 0.7 g/kg versus 0.3 g/kg: MD 1.30 stools/week (95% CI 0.76 to 1.84)
• Funding: not stated.

Participants receiving high dose PEG (0.7 g/kg) had significantly more stools per week than low dose PEG (0.3 g/kg) participants (1 study, 90 participants, MD 1.30, 95% 0.76 to 1.84).

In IBS-C, PEG 3350 plus electrolytes increased spontaneous bowel movements compared with placebo. (Source 5)

• Randomized trial, Moderate certainty.
• Size: 139 randomised (PEG 3350+E n=68, placebo n=71)
• Who: adults with Rome-confirmed constipation-predominant IBS.
• How long: 28 days after a 14-day run-in.
• Result: mean SBMs in week 4: 4.40 (SD 2.581) with PEG 3350+E versus 3.11 (SD 1.937) with placebo; 95% CI of the difference 1.17 to 1.95; P<0.0001.
• Funding: not stated in the record we read; the trial tested a branded PEG 3350 plus electrolytes product, so industry sponsorship should be assumed until checked.

The difference between the groups in week 4 (PEG 3350+E, 4.40±2.581; placebo, 3.11±1.937) was statistically significant (95% confidence interval: 1.17, 1.95; P<0.0001).

What the evidence does not support

Adding electrolytes to polyethylene glycol produced no measurable extra efficacy, safety or tolerability benefit. (Source 3)

• Meta-analysis, Moderate certainty.
• Size: 2 head-to-head studies within the 19-study network (2,247 patients overall)
• Who: adults with functional constipation.
• How long: short-term trials.
• Result: difference in mean bowel movements per week PEG+E minus PEG 0.1 (95% Crl -1.1, 1.2); direct head-to-head comparison -0.5 (95% Crl -4.5, 3.3)
• Funding: medical writing and statistics funded by Key Pharmaceuticals Pty Ltd, a manufacturer of PEG without electrolytes - a funder with an interest in this result, which a reader should weigh.

There was no efficacy difference between PEG + E and PEG (0.1, 95 % Crl -1.1, 1.2) and there were no differences in safety or tolerability.

In children, PEG was no better than dietary fibre, flixweed, liquid paraffin or enemas for stools per week. (Source 18)

• Systematic review, Very low certainty.
• Size: single or paired small trials (83 to 261 participants per comparison)
• Who: children with functional constipation.
• How long: short follow-up.
• Result: PEG versus enemas MD 1.00 (95% CI -1.58 to 3.58); PEG versus dietary fibre MD 0.20 (95% CI -0.64 to 1.04); PEG versus liquid paraffin MD 0.35 (95% CI -0.24 to 0.95)
• Funding: not stated in the review record we read.

No statistically significant differences in the number of stools per week were found between PEG and enemas (1 study, 90 patients, MD 1.00, 95% CI -1.58 to 3.58)

In IBS-C, PEG 3350 plus electrolytes did not improve abdominal discomfort or pain compared with placebo. (Source 5)

• Randomized trial, Moderate certainty.
• Size: 139 randomised.
• Who: adults with constipation-predominant IBS.
• How long: 28 days.
• Result: abdominal discomfort/pain improved versus the patient's own run-in but showed no difference versus placebo.
• Funding: not stated in the record we read; branded product trial.

Although mean severity score for abdominal discomfort/pain was significantly reduced compared with run-in with PEG 3350+E, there was no difference vs. placebo.

Where the evidence is mixed

Only four of the trials pooled in the network meta-analysis were judged at low risk of bias, and no trial reported specifically on older people. (Source 9)

• Meta-analysis, Low certainty.
• Size: 19 studies, 2,247 patients.
• Who: adults with functional constipation.
• How long: short-term.
• Result: 4 of 20 qualifying studies at low risk of bias; planned age-related subanalysis abandoned for lack of data.
• Funding: medical writing and statistics funded by Key Pharmaceuticals Pty Ltd.

There were only four studies considered to have a low risk of bias.

Cochrane judged the overall certainty of the childhood-constipation evidence low or very low because of sparse data, heterogeneity and high risk of bias. (Source 13)

• Systematic review, Very low certainty.
• Size: 25 trials, 2,310 participants; 14 trials at high risk of bias.
• Who: children with functional constipation.
• How long: short follow-up.
• Result: GRADE rating low or very low for the primary outcome (stools per week)
• Funding: not stated in the review record we read.

GRADE analyses indicated that the overall quality of the evidence for the primary outcome (number of stools per week) was low or very low due to sparse data, inconsistency (heterogeneity), and high risk of bias in the studies in the pooled analyses.

Adequate bowel cleansing was achieved in only about half of hospitalised patients with either regimen. (Source 16)

• Randomized trial, Moderate certainty.
• Size: 520 randomised.
• Who: hospitalised adults undergoing colonoscopy.
• How long: single preparation.
• Result: adequate preparation 55.0% with 2L PEG+ASC versus 52.9% with 4L PEG-ELS (per-protocol, non-inferiority P=0.007)
• Funding: not stated in the record we read.

In per-protocol analysis, 2L PEG+ASC was noninferior to 4L PEG-ELS for achievement of adequate bowel preparation (55.0% vs. 52.9%, P =0.007).

Concern that low-molecular-weight glycols are absorbed from PEG 3350 in children was tested directly; diethylene and triethylene glycol were below the limit of quantitation. (Source 19)

• Blood level study, Very low certainty.
• Size: a pilot study of children taking PEG 3350 (number not given in the record we read)
• Who: children taking PEG 3350.
• How long: not stated.
• Result: analytical range 2-20 mcg/mL; DEG and TEG detected below the limit of quantitation.
• Funding: not stated.

The validated methods were applied to analyze samples a pilot study of children taking PEG 3350. DEG and TEG were detected at levels below the limit of quantitation.

Where the research disagrees

Whether adding electrolytes to PEG 3350 is worth it for everyday constipation

• Katelaris and colleagues, network meta-analysis of 19 trials (2016), systematic review and Bayesian network meta-analysis of randomised trials, with the medical writing and statistics funded by a manufacturer of PEG without electrolytes: There was no efficacy difference between PEG + E and PEG (0.1, 95 % Crl -1.1, 1.2) and there were no differences in safety or tolerability. (Source 3)
• The US GoLYTELY label (Azurity Pharmaceuticals, revised 1/2026), regulatory position: the electrolyte-containing formulation is the approved one for colon cleansing, where the salts are there to limit net fluid and salt shifts at lavage volumes: GoLYTELY is a combination of PEG 3350, an osmotic laxative, and electrolytes indicated for cleansing of the colon in preparation for colonoscopy and barium enema X-ray examination in adults. (Source 2)

How good the evidence in children really is

• Cochrane reviewers (Gordon and colleagues, 2016) on the effect, meta-analysis of two small placebo-controlled trials (101 children): Meta-analysis of two studies (101 patients) comparing polyethylene glycol (PEG) with placebo showed a significantly increased number of stools per week with PEG (MD 2.61 stools per week, 95% CI 1.15 to 4.08). (Source 4)
• The same Cochrane reviewers on the certainty of that effect, GRADE assessment of the same pooled analyses: GRADE analyses indicated that the overall quality of the evidence for the primary outcome (number of stools per week) was low or very low due to sparse data, inconsistency (heterogeneity), and high risk of bias in the studies in the pooled analyses. (Source 13)

How much

• Reference intake: There is no reference intake for PEG 3350 with electrolytes because it is a medicine, not a nutrient. The dose is set by the prescriber or, for over-the-counter macrogol products, by the product labelling. As a regulatory position, the US GoLYTELY label (revised 1/2026) directs 8 ounces every 10 minutes until 4 litres are drunk or the rectal effluent is clear. (Source 2)
• Upper limit: No tolerable upper intake level exists for a laxative. The label's own ceiling for bowel cleansing is one 4 litre course, made up from 236 g PEG 3350 with 22.74 g sodium sulfate, 6.74 g sodium bicarbonate, 5.86 g sodium chloride and 2.97 g potassium chloride; that is a position of the label holder dated 1/2026, not a safety threshold derived from toxicology. (Source 20)
• Studied: Bowel cleansing: 4 litres of PEG 3350 with electrolytes drunk as 8 ounces every 10 minutes, versus 2 litres of PEG plus ascorbate, in 520 hospitalised adults. (Source 16)
• Studied: Children with functional constipation: PEG 0.7 g/kg/day compared with 0.3 g/kg/day in one 90-participant trial. (Source 4)
• Studied: IBS-C: PEG 3350 plus electrolytes versus placebo for 28 days in 139 adults (the trial record we read does not state the daily dose). (Source 5)

A common belief, and what the research shows

The belief: The electrolytes in “PEG 3350 with electrolytes” make it safer or more effective than plain PEG 3350.

What the research shows: For everyday constipation the pooled randomised evidence says otherwise. The 2016 network meta-analysis reports “There was no efficacy difference between PEG + E and PEG (0.1, 95 % Crl -1.1, 1.2) and there were no differences in safety or tolerability.” and concludes the addition of electrolytes “does not appear to offer any clinical benefits over polyethylene glycol alone”. More patients stopped the electrolyte version for side effects (1.8% versus 0.4%). The electrolytes earn their place at lavage volumes, where the salts limit net fluid and salt shifts, which is the setting the US label approves them for.

Questions and answers

What is it?

It is a powder dissolved in water and drunk. The working ingredient is polyethylene glycol 3350, a synthetic water-binding polymer that the gut barely absorbs and gut bacteria cannot ferment. Mixed in with it are sodium and potassium salts: a 4 litre bowel-cleansing jug holds 236 g of PEG 3350 with 22.74 g sodium sulfate, 6.74 g sodium bicarbonate, 5.86 g sodium chloride and 2.97 g potassium chloride. European sachet products for constipation contain the same ingredients in much smaller amounts. (Source 20)

What does it do in the body?

It keeps water in the bowel. Because PEG 3350 binds the water that has been swallowed and is not charged, it increases the water content of stool without pulling water out of the body, so stool softens and the bowel empties. At bowel-cleansing volumes the same mechanism produces watery diarrhoea that clears the colon, usually within about four hours. (Source 1)

Is it good or bad for you?

Good in context, and the context matters. For clearing the colon before a colonoscopy it is the standard treatment. For constipation, pooled randomised trials show about two extra bowel movements a week versus placebo, and it beats lactulose. It does not help abdominal pain in IBS. The bad side is dose-dependent: at everyday laxative doses harms are mostly bloating, cramps, nausea and loose stools, but the litres needed for bowel cleansing can disturb fluid and salts enough to cause seizures, arrhythmias and kidney injury, and PEG itself can trigger anaphylaxis. Children and older people with heart or kidney disease are the groups where the evidence is thinnest and the risk highest. (Source 21)

How do you get more of it?

This question does not really apply: it is a medicine, not a nutrient, and nobody needs more of it than a clinician or the product label directs. In the US the electrolyte-containing bowel-cleansing solutions are prescription-only; plain PEG 3350 without electrolytes is sold over the counter, and macrogol 3350 with electrolytes is sold as pharmacy sachets in the UK and Europe. No food or behaviour increases it. (Source 22)

If it is harmful, what reduces it?

There is nothing to clear from the body. PEG 3350 is biologically inert, is not metabolised by colonic bacteria and is poorly absorbed, so it passes out in the stool; its laxative effect ends when dosing stops. If the problem is the salt and water shift rather than the polymer, the treatment is rehydration and correction of electrolytes, which is what resolved the reported seizure cases. (Source 23)

Why might someone be low in it or missing it?

This does not apply. It is a manufactured medicine, not something the body makes or needs, so there is no deficiency state and no reason a person would be “low” in it. What varies is how well it works: it is not absorbed and not fermented, so its effect depends on dose and on how much fluid is taken with it rather than on the body's own stores. (Source 23)

Which whole foods contain it or feed it?

No whole food contains PEG 3350, and no food feeds it - gut bacteria cannot ferment it, which is why it causes less gas than sugar-based laxatives such as lactulose. The dietary comparators that have been tested against it in children are dietary fibre and flixweed, and in those small trials PEG was no better than fibre for stools per week. (Source 13)

What happens if you do not have it?

Nothing happens from not taking it - there is no deficiency. The relevant question is what happens if constipation goes untreated. Constipation affects about 15 to 17% of the general population, rises to around 81% of older hospitalised patients and 95% of people taking opioids, and worsens quality of life; untreated, the pooled trials show stool frequency stays at the placebo level, roughly two bowel movements a week lower than on treatment. (Source 1)

How can you test for it?

There is no clinical test for PEG 3350 itself, and none is needed. What is monitored is the consequence: the label advises baseline and post-procedure electrolytes, creatinine and BUN in people with kidney impairment or on drugs that affect the kidney. One research group has validated GC-MS assays for ethylene, diethylene and triethylene glycol in blood and urine to test the theory that glycols are absorbed from PEG 3350 in children; in their pilot samples these were below the limit of quantitation. (Source 24)

References

1. BMC Gastroenterology. Comparison of the effectiveness of polyethylene glycol with and without electrolytes in constipation: a systematic review and network meta-analysis. 2016. PMID 27029340, DOI 10.1186/s12876-016-0457-9. Read the source
2. DailyMed / US National Library of Medicine (label holder Azurity Pharmaceuticals). GOLYTELY (polyethylene glycol 3350 and electrolytes for oral solution) - US prescribing information, revised 1/2026. 2026. Read the source
3. BMC Gastroenterology. Comparison of the effectiveness of polyethylene glycol with and without electrolytes in constipation: a systematic review and network meta-analysis. 2016. PMID 27029340, DOI 10.1186/s12876-016-0457-9. Read the source
4. Cochrane Database of Systematic Reviews. Osmotic and stimulant laxatives for the management of childhood constipation. 2016. PMID 27531591, DOI 10.1002/14651858.CD009118.pub3. Read the source
5. The American Journal of Gastroenterology. Randomized clinical trial: macrogol/PEG 3350 plus electrolytes for treatment of patients with constipation associated with irritable bowel syndrome. 2013. PMID 23835436, DOI 10.1038/ajg.2013.197. Read the source
6. DailyMed / US National Library of Medicine (label holder Azurity Pharmaceuticals). GOLYTELY (polyethylene glycol 3350 and electrolytes for oral solution) - US prescribing information, revised 1/2026. 2026. Read the source
7. DailyMed / US National Library of Medicine (label holder Azurity Pharmaceuticals). GOLYTELY (polyethylene glycol 3350 and electrolytes for oral solution) - US prescribing information, revised 1/2026. 2026. Read the source
8. DailyMed / US National Library of Medicine (label holder Azurity Pharmaceuticals). GOLYTELY (polyethylene glycol 3350 and electrolytes for oral solution) - US prescribing information, revised 1/2026. 2026. Read the source
9. BMC Gastroenterology. Comparison of the effectiveness of polyethylene glycol with and without electrolytes in constipation: a systematic review and network meta-analysis. 2016. PMID 27029340, DOI 10.1186/s12876-016-0457-9. Read the source
10. DailyMed / US National Library of Medicine (label holder Azurity Pharmaceuticals). GOLYTELY (polyethylene glycol 3350 and electrolytes for oral solution) - US prescribing information, revised 1/2026. 2026. Read the source
11. DailyMed / US National Library of Medicine (label holder Azurity Pharmaceuticals). GOLYTELY (polyethylene glycol 3350 and electrolytes for oral solution) - US prescribing information, revised 1/2026. 2026. Read the source
12. BMC Gastroenterology. Comparison of the effectiveness of polyethylene glycol with and without electrolytes in constipation: a systematic review and network meta-analysis. 2016. PMID 27029340, DOI 10.1186/s12876-016-0457-9. Read the source
13. Cochrane Database of Systematic Reviews. Osmotic and stimulant laxatives for the management of childhood constipation. 2016. PMID 27531591, DOI 10.1002/14651858.CD009118.pub3. Read the source
14. BMC Gastroenterology. Comparison of the effectiveness of polyethylene glycol with and without electrolytes in constipation: a systematic review and network meta-analysis. 2016. PMID 27029340, DOI 10.1186/s12876-016-0457-9. Read the source
15. BMC Gastroenterology. Comparison of the effectiveness of polyethylene glycol with and without electrolytes in constipation: a systematic review and network meta-analysis. 2016. PMID 27029340, DOI 10.1186/s12876-016-0457-9. Read the source
16. Journal of Clinical Gastroenterology. Efficacy and Safety of Low Volume Bowel Preparation for Colonoscopy in Hospitalized Patients: A Randomized Noninferiority Trial. 2025. PMID 41128725, DOI 10.1097/MCG.0000000000002269. Read the source
17. The American Journal of Case Reports. Recurrent Severe Hyponatremia Following Polyethylene Glycol Electrolyte Lavage Solution with Ascorbic Acid in a Patient with Undiagnosed Syndrome of Inappropriate Antidiuretic Hormone Secretion. 2025. PMID 40760784, DOI 10.12659/AJCR.948355. Read the source
18. Cochrane Database of Systematic Reviews. Osmotic and stimulant laxatives for the management of childhood constipation. 2016. PMID 27531591, DOI 10.1002/14651858.CD009118.pub3. Read the source
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20. DailyMed / US National Library of Medicine (label holder Azurity Pharmaceuticals). GOLYTELY (polyethylene glycol 3350 and electrolytes for oral solution) - US prescribing information, revised 1/2026. 2026. Read the source
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