Glucagon-like peptide-1 (GLP-1) receptor agonists such as semaglutide (Ozempic, Wegovy) and dulaglutide (Trulicity) are increasingly prescribed for type 2 diabetes and weight management across the UK. Whilst these medications offer significant metabolic benefits, constipation is a commonly reported side effect due to delayed gastric emptying. Finding the best stool softener for GLP-1 users requires understanding which laxatives work effectively alongside these medications. This article examines evidence-based options available in the UK, including macrogol preparations, bulk-forming laxatives, and docusate sodium, alongside practical guidance on safe use and lifestyle modifications to support bowel health during GLP-1 therapy.

Why GLP-1 Medications Can Cause Constipation

Glucagon-like peptide-1 (GLP-1) receptor agonists, including semaglutide (Ozempic, Wegovy), dulaglutide (Trulicity), and liraglutide (Victoza, Saxenda), have become widely prescribed for type 2 diabetes management and weight loss. Whilst these medications offer significant metabolic benefits, gastrointestinal side effects—particularly constipation—are commonly reported by patients.

The primary mechanism underlying GLP-1-induced constipation relates to how these drugs slow gastric emptying, meaning food moves more gradually from the stomach into the small intestine. This delayed transit is therapeutically beneficial, as it promotes satiety and helps regulate blood glucose levels. This effect may also influence overall gut transit time, potentially contributing to constipation in some patients.

Constipation is a recognised adverse effect listed in the Summary of Product Characteristics for all GLP-1 medications. The severity varies considerably between individuals, with some experiencing mild infrequent bowel movements and others developing significant discomfort requiring intervention. Some patients notice constipation during dose escalation phases, whilst others develop more persistent symptoms.

Not all patients will experience constipation while taking GLP-1 medications. Those with pre-existing bowel conditions, inadequate fluid intake, sedentary lifestyles, or taking other constipating medications (such as opioids, iron supplements, or certain antidepressants) may be at higher risk. Understanding these factors helps patients and healthcare professionals implement appropriate preventative and management strategies.

Best Stool Softeners for GLP-1 Users in the UK

When lifestyle modifications prove insufficient, laxatives can provide effective relief for GLP-1-related constipation. In the UK, several evidence-based options are available over-the-counter or on prescription, each with distinct mechanisms of action.

Bulk-forming laxatives such as ispaghula husk (Fybogel) and sterculia (Normacol) are generally recommended as first-line treatment for constipation with hard stools according to NICE Clinical Knowledge Summaries. These work by absorbing water and increasing faecal mass, stimulating peristalsis. They should be taken with plenty of fluid and may take 2-3 days to work. Start with a low dose and increase gradually to minimise bloating.

Macrogol (polyethylene glycol) preparations such as Laxido, Movicol, and CosmoCol are osmotic laxatives that retain water in the stool, increasing its bulk and softness. These are commonly used and effective for chronic constipation. Macrogols are typically taken as one to three sachets daily, dissolved in water. They are well-tolerated for long-term use and are particularly useful for patients on GLP-1 medications. For faecal impaction, higher doses (up to 8 sachets daily) may be used under medical supervision.

Docusate sodium (Docusol, DulcoEase) is a stool softener that works by increasing water and fat penetration into the stool. Typical dosing is 100–300 mg daily in divided doses, with a maximum of 500 mg daily. It may take 1–3 days to produce effects and has relatively modest efficacy compared to other laxatives.

Lactulose is another osmotic laxative that draws water into the bowel. The usual dose is 15 ml twice daily, adjusted according to response. It can cause bloating and flatulence in up to 20% of patients, which may be problematic for those already experiencing GLP-1-related gastrointestinal symptoms. It should be avoided in patients with galactosaemia.

Stimulant laxatives such as bisacodyl (Dulcolax) and senna increase bowel contractions. They provide faster relief (typically within 6–12 hours) and are useful for occasional constipation. While traditionally recommended for short-term use, some patients may require longer-term supervised use as part of a bowel management plan.

Glycerol suppositories can provide local stimulation and lubrication when oral treatments are insufficient or rapid relief is needed.

Patients should consult their GP or pharmacist before starting any laxative, particularly if taking multiple medications or experiencing severe symptoms such as abdominal pain, rectal bleeding, or prolonged constipation.

How to Use Stool Softeners Safely with GLP-1 Treatment

Safe and effective use of laxatives alongside GLP-1 therapy requires understanding proper dosing, timing, and potential interactions. Patients should always read the patient information leaflet and follow healthcare professional advice tailored to their individual circumstances.

Starting treatment: Begin with the lowest effective dose and increase gradually if needed. For bulk-forming laxatives, start with a single dose daily before gradually increasing. With macrogol preparations, starting with one sachet daily and increasing to two or three sachets based on response is a sensible approach. This stepwise approach minimises the risk of bloating, diarrhoea or abdominal cramping.

Timing considerations: Most laxatives can be taken at any time of day, though consistency helps establish a routine. Macrogols are best taken with meals or shortly afterwards. Ensure adequate fluid intake—at least 1.5–2 litres daily—as both GLP-1 medications and laxatives require sufficient hydration to work effectively. Patients with heart failure, kidney disease or other conditions requiring fluid restriction should follow their healthcare professional's advice about fluid intake.

Drug interactions: Macrogol laxatives may reduce the absorption of other oral medications. Take other medicines at least 1–2 hours before or after macrogol preparations. While injectable GLP-1 medications themselves are unlikely to have clinically significant interactions with laxatives, they may delay absorption of other oral medications due to slowed gastric emptying.

Monitoring and adjustment: Keep a bowel diary noting frequency, consistency (using the Bristol Stool Chart as reference), and any associated symptoms. Aim for soft, formed stools (Bristol Type 4) passed comfortably every 1–3 days. If diarrhoea develops, reduce the laxative dose. If constipation persists despite maximum recommended doses for 1–2 weeks, contact your GP for review.

When to seek medical advice: Patients should contact their healthcare provider if they experience severe abdominal pain, rectal bleeding, unexplained weight loss, persistent vomiting, or if constipation does not improve with over-the-counter treatment within 1–2 weeks. These symptoms may indicate complications requiring further investigation.

Special considerations: Pregnant or breastfeeding women should consult their healthcare provider before using laxatives. If constipation is particularly troublesome, discuss with your prescriber whether adjusting your GLP-1 medication dose or slowing the titration schedule might help manage symptoms while maintaining therapeutic benefits.

Lifestyle Changes to Support Bowel Health on GLP-1 Therapy

Whilst laxatives provide symptomatic relief, addressing underlying lifestyle factors is essential for long-term bowel health during GLP-1 treatment. Evidence-based non-pharmacological strategies can significantly reduce constipation severity and may decrease reliance on laxatives.

Dietary fibre optimisation: Gradually increase dietary fibre intake to 25–30 grams daily through wholegrains, fruits, vegetables, pulses, and seeds. Soluble fibre (found in oats, apples, and psyllium husk) and insoluble fibre (in wheat bran, nuts, and vegetables) both contribute to healthy bowel function. However, increase fibre gradually over 2–3 weeks to avoid bloating, which can be particularly uncomfortable for patients experiencing GLP-1-related delayed gastric emptying. Ensure adequate fluid intake when increasing fibre. Prunes and kiwifruit have specific evidence supporting their laxative effects and can be incorporated into daily diet.

Hydration: Adequate fluid intake is crucial, particularly when using laxatives or increasing dietary fibre. Aim for at least 1.5–2 litres of water daily, more in hot weather or during exercise, unless you have been advised to restrict fluids due to a medical condition. Caffeinated beverages can have a mild stimulant effect on the bowel but should not replace water as the primary fluid source.

Physical activity: Regular exercise stimulates intestinal motility and can significantly improve constipation. The UK Chief Medical Officers recommend at least 150 minutes of moderate-intensity activity weekly. Even gentle activities such as walking, swimming, or yoga can benefit bowel function. Establishing a routine that includes post-meal walking may be particularly helpful, as physical activity after eating can promote gastric emptying and intestinal transit.

Bowel routine establishment: Respond promptly to the urge to defaecate rather than delaying, as ignoring these signals can worsen constipation. Allow adequate time for bowel movements without straining. Some patients find establishing a regular time—often after breakfast when the gastrocolic reflex is strongest—helps maintain consistency. Proper toilet posture, with feet elevated on a small stool to create a squatting position, can facilitate easier evacuation.

Medication review: Discuss all medications with your GP or pharmacist, as some commonly prescribed drugs (including certain antihypertensives, antidepressants, iron supplements, and opioid painkillers) can contribute to constipation. Where possible, alternatives may be considered. Never stop prescribed medications without medical advice, but a comprehensive medication review may identify opportunities for optimisation that benefit both your primary condition and bowel health.

If you experience side effects from any medication, including GLP-1 receptor agonists, you can report them through the MHRA Yellow Card scheme.

Frequently Asked Questions