Wegovy and Liquid Diarrhoea: What's Happening and What to Do

Why does Wegovy cause loose or watery stools in the first place?

Semaglutide, the active ingredient in Wegovy, works by activating GLP-1 receptors that regulate appetite and slow the rate at which food moves through the stomach. That slowing of gastric emptying changes the rhythm of the entire digestive system, and for some people the downstream effect is looser, faster bowel movements rather than constipation. Both responses sit at opposite ends of the same mechanism.

A common misconception is that liquid diarrhoea on Wegovy means the medicine isn't working, or that something has gone wrong with the prescription. In most cases it simply reflects how sensitive a particular person's gut is to the change in motility. The NHS medicines page for semaglutide lists diarrhoea among the most frequently reported side effects, alongside nausea, constipation and indigestion. Liquid stools are the more intense presentation of that same category.

Dose increases are a particular trigger. When you step up from one strength to the next, the gut receives a stronger signal before it has fully adapted. Most people who experience watery stools notice them most acutely in the first week after a step-up. If you want a broader picture of how diarrhoea fits into the wider side-effect profile, our guide to Wegovy side effects covers the full range.

How long does liquid diarrhoea from Wegovy typically last?

For the majority of people, loose or liquid stools settle within a few days to roughly two weeks. The gut adjusts to the new rate of gastric emptying, and bowel habits normalise. That pattern holds both when starting treatment and after each dose increase.

There is no hard rule about exactly how many days you'll experience symptoms, because individual variation is real. Factors that influence duration include how quickly you titrated, what you're eating alongside treatment, hydration levels and general gut sensitivity. Eating smaller meals, avoiding fatty or very rich food and keeping well hydrated all tend to shorten the uncomfortable phase. Our page on foods to avoid when diarrhoea is a problem on Wegovy goes into the dietary detail.

If liquid stools are persisting beyond two weeks without improvement, or if they return with each new dose increase and never fully settle, that is a pattern worth discussing with your prescriber rather than waiting out. The prescriber can assess whether slower titration or other adjustments would help. You can explore more about persistent symptoms and patterns on our page covering diarrhoea after Wegovy.

When does liquid diarrhoea on Wegovy become a medical concern?

Most cases are unpleasant but manageable. Some are not. Dehydration is the main risk from prolonged or very frequent watery stools, and it can develop faster than people expect, particularly in hot weather or when nausea is also reducing fluid intake. Signs that dehydration is developing include a dry mouth, dark urine, dizziness on standing and feeling much more fatigued than usual.

Seek prompt medical attention if you experience any of the following: diarrhoea that is very frequent or completely liquid for more than 24 hours without improvement; signs of dehydration you cannot correct by drinking; blood in your stool; severe stomach cramps that are getting worse rather than easing; or symptoms that began after starting a new medicine alongside Wegovy. Kidney function can be affected by significant fluid loss, which is why the management of severe diarrhoea on Wegovy deserves proper clinical attention rather than self-management alone.

If you're unsure whether your symptoms need medical review, contact your prescriber or your GP. For out-of-hours advice, NHS 111 is available. Suspected side effects that feel serious can also be reported directly through the MHRA Yellow Card scheme, which exists partly so regulators can track patterns across many patients.

What can you actually do to manage liquid diarrhoea while staying on treatment?

Practical steps make a genuine difference for most people. Hydration comes first: water, diluted squash and oral rehydration sachets all help replace what's lost. Small, low-fat meals are easier on a gut that's already unsettled. High-fibre foods and very rich or spicy dishes are worth avoiding during a flare. Some people find that timing meals carefully around their injection day helps.

Over-the-counter loperamide is sometimes used for symptomatic relief of diarrhoea, but it's worth discussing with a pharmacist or your prescriber before using it regularly on a GLP-1 medicine, as interactions and underlying causes need to be ruled out first. Never adjust your Wegovy dose yourself to manage a side effect. The prescriber who reviewed your consultation makes that call based on the full picture.

For a comparison of how diarrhoea patterns differ between semaglutide and other GLP-1 options, the Wegovy versus Saxenda side-effect comparison is worth reading. And if you're still deciding whether Wegovy is right for you at all, our full Wegovy overview covers the medicine from the beginning. At nume, side effects like these are part of every consultation discussion, not an afterthought.