Can You Get Diarrhoea from Wegovy — and What Can You Do About It?

The misconception worth clearing up first

A lot of people assume diarrhoea means the medicine is failing, or that their body is rejecting it, and stop treatment earlier than they need to. That is a common reaction (and an understandable one) but it is not usually what is happening. Loose stools in the early weeks of Wegovy are almost always a pharmacological response to semaglutide slowing the speed at which food leaves the stomach, not a sign the medicine is wrong for you.

Slowing gastric emptying changes how quickly contents move through the gut. For some people that produces constipation; for others (especially at the start) the shift in gut motility tips the other way. The NHS medicines page for semaglutide lists diarrhoea explicitly among the common side effects, meaning it occurs in more than one in a hundred people. In clinical trials it was reported frequently, particularly at lower escalation doses before the gut adapts.

The dose matters. Diarrhoea tends to peak around the time a new dose starts and then ease. If you have just moved up from 1.0 mg to 1.7 mg, or from 1.7 mg to 2.4 mg, a few days of looser stools is not unusual. Knowing that in advance often makes it easier to sit with rather than panic about. People starting out may also find it helpful to read about what to expect from the earliest Wegovy dose, where GI symptoms are often at their most noticeable. More detail on how GI symptoms track through the full Wegovy side-effect profile may help put it in context.

How bad is it likely to be, and how long does it last?

For most people, diarrhoea on Wegovy is mild to moderate and resolves within a week or two of a stable dose. It tends not to be the debilitating kind that keeps you housebound, though that is not guaranteed. Staying well hydrated is the single most practical thing you can do while it is happening, small, frequent sips rather than large glasses if nausea is also present.

Eating smaller portions and avoiding very fatty or rich meals during the first weeks at each dose can reduce the load on a slowed digestive system. Plain, low-fat foods are easier to process. This is not about following a rigid diet; it is about giving your gut a quieter period while it adjusts. There is more on why semaglutide causes diarrhoea physiologically if the mechanism is useful to understand.

If it lasts beyond two to three weeks at a stable dose, or is frequent enough to disrupt daily life, that is worth a conversation with your prescribing team rather than something to tolerate silently. Persistent diarrhoea can interfere with how well your body absorbs other medicines, including oral contraceptives, so it is relevant information for your prescriber to have. Anyone wanting a closer look at how diarrhoea from Wegovy tends to present and progress will find a dedicated guide there. People who want the broader picture of how Wegovy works as a treatment will find an overview there.

When to get medical help

Most diarrhoea on Wegovy does not require a trip to A&E. But some scenarios do. Seek urgent medical attention if you experience any of the following: severe stomach pain that spreads to your back, with or without vomiting (this combination can indicate pancreatitis, which the MHRA flagged in a Drug Safety Update in January 2026 as an infrequent but serious risk with GLP-1 medicines); signs of dehydration such as very dark urine, dizziness on standing, or noticeably reduced urination; diarrhoea that is bloody or contains mucus; or symptoms that are getting worse rather than better after several days.

Dehydration from prolonged diarrhoea can place strain on the kidneys, particularly in people who are also taking medicines that affect kidney function. This is not a reason to avoid Wegovy, but it is a reason to take persistent symptoms seriously. If you are unsure whether your symptoms warrant a call, the safest default is to contact your prescriber or GP. You can also read more about whether semaglutide is likely to cause diarrhoea for you specifically, including factors that influence individual risk. You can also report suspected side effects through the MHRA's Yellow Card scheme, doing so contributes to the ongoing real-world safety monitoring of newer medicines.

If you are considering Wegovy and side effects are a deciding factor, our prescribers at nume's clinical team discuss the full side-effect picture as part of every consultation, not as a formality, but because it shapes whether the medicine suits you and how to start at the right pace. You can check your eligibility and start that conversation at no cost.