How Long Does Diarrhoea Last When Taking Wegovy — and When Should You Act?

Step 1: The first one to two weeks at a new dose

The most common pattern is a burst of loose stools or diarrhoea in the days immediately after starting Wegovy at 0.25 mg or after each upward dose step. Semaglutide acts on GLP-1 receptors in the gut wall as well as the brain, slowing gastric emptying and altering bowel motility, a process the body has not encountered before. The gut tends to respond noisily at first.

For many people symptoms are mild and manageable: one or two loose stools a day, perhaps some urgency, often coinciding with when the injection takes its strongest effect in the first 24 to 48 hours after each weekly dose. If you are wondering how long Wegovy diarrhoea typically lasts, keeping a simple note of timing helps, because if your symptoms seem to cluster around injection day, that is consistent with the pharmacology of the medicine rather than a coincidental illness.

Practical habits that can make this stage easier include eating smaller portions, avoiding high-fat or very spicy meals and cutting back on caffeine temporarily. The NHS semaglutide medicines page describes these as commonly reported effects that typically ease over time. If you keep Wegovy in the fridge door, a small note there to remind yourself to eat lightly on injection days is the kind of low-effort prompt that patients often find genuinely useful.

Step 2: Weeks two to four, what 'settling' looks like

By the second or third week at a stable dose, most people find the frequency and severity of diarrhoea reduces noticeably. The gut adapts to slowed motility, and the initial over-correction towards loose stools gives way to a more predictable pattern. Some people find their bowel habits normalise completely at this stage; others notice that symptoms reappear briefly with each dose increase before settling again.

This is also the window where it becomes important to distinguish ordinary adjustment from something that needs attention. Diarrhoea that remains frequent and watery beyond two weeks at a stable dose, or that is severe enough to affect daily life, is worth discussing with your prescriber rather than waiting out. The broader side-effect timeline for Wegovy (covering nausea, constipation and other GI effects) is covered in detail in our guide to how long Wegovy's side effects last.

Hydration matters most here. Diarrhoea causes fluid loss faster than many people expect; rehydration solutions (available from any pharmacy) are preferable to plain water when symptoms are frequent, because they replace electrolytes as well as fluid. Alcohol and high-sugar drinks tend to worsen symptoms and are worth avoiding.

When to get medical help, signs that go beyond normal adjustment

Certain symptoms should prompt you to contact a doctor or, if severe, attend urgent care rather than waiting for your next prescriber check-in. Diarrhoea that is accompanied by severe or persistent stomach pain (especially pain that radiates towards the back) is a reason to seek medical attention promptly. The MHRA's 2026 Drug Safety Update on GLP-1 medicines identified acute pancreatitis as an infrequent but serious risk; severe abdominal pain with or without vomiting should never be put down to routine GI upset without medical assessment.

Other reasons to contact a clinician include: diarrhoea lasting more than a week at the same dose without any improvement; signs of dehydration such as dizziness, markedly reduced urine output or a rapid heartbeat; blood in stools; and fever alongside GI symptoms, which may point to an unrelated infection. If you are already unwell for another reason and wondering how that interacts with your treatment, our guidance on taking Wegovy when you're sick covers that scenario specifically.

Patients sometimes ask whether they should skip a dose when diarrhoea is severe. That is a clinical decision (not one to make from guidance alone) so the right step is to contact your prescribing team. At nume, our clinical team provides aftercare seven days a week; any prescriber-level question can be directed there rather than guessed at.

Diarrhoea that persists across multiple dose levels

A minority of people find that loose stools or diarrhoea remain a recurring feature throughout treatment rather than fading between dose steps. This is worth raising rather than tolerating, because a prolonged slower titration schedule or a different management approach may be appropriate, and because persistent GI symptoms are one of the common reasons people discontinue a medicine that could otherwise benefit them.

There is also a less-discussed cause of loose stools on semaglutide: sulphurous or 'eggy' burping, followed by nausea and loose stools, can signal a specific GI response that some people find more distressing than plain diarrhoea. If that pattern sounds familiar, the detail is covered in our explanation of Wegovy and sulphurous burps. Separately, nausea often accompanies diarrhoea in the early weeks; the timeline for that symptom is different, and our page on Wegovy nausea duration addresses it directly.

Wegovy is a prescription medicine (semaglutide, made by Novo Nordisk) licensed in the UK for weight management in adults with a BMI of 30 or above, or 27 or above with a weight-related health condition. The NHS England weight management injections guidance outlines how the medicine is used in clinical practice. Whether the side-effect profile of semaglutide is right for you individually is exactly the kind of question our prescribers work through as part of a consultation, you can check your eligibility and start a free consultation if you're considering treatment.